I don't mean to brag, but I'm pretty good at Rock Band Blitz. As of the time I write this, a week following release, I'm still sitting in the top 2% of (Xbox 360) players across all of the songs packaged with the game, have about a hundred tracks I've earned Gold Stars on and am 9 for 2 in my Score Wars. I was also, near as I can tell, the first person in the world to earn the "Precious Medal" Achievement (awarded for Gold Stars in all 25 Blitz songs).
Okay, maybe I did mean to brag with that last bit.
The point is, I do a pretty good job of scoring lots of points in Rock Band Blitz and I'd like to help you to do it too. Here are some guidelines to follow when you want to bring your best game.
Get experimental with the controls
Now, this might seem like a really obvious statement, but hear me out. Take some time to play with all of the available control options and find the one which works best for you. I'm a Freakish player, personally, preferring to tap with my index fingers on the bumpers and switch tracks with the left analog stick, but what works for me may not suit you.
I suggest you even go beyond just fiddling through the menus. If you're a Rock Band player, you have plastic instruments lying around. Switch the controls to Typewriter and try playing the game with your guitar or keyboard. Have a fight stick? Try that. Hell, I even turned my fight stick upside down to use the reversed bumper and trigger buttons in combination with the Shoulders configuration to play it. They'll work, it's just a question of whether or not they'll work for you.
A miserly youth enables a generous old age
If, for whatever reason, you haven't yet unlocked the full range of power-ups yet, I wouldn't rush into using them. They're fun to play with, but when you run out of cash while you're trying to drill out that last 10k from a song and have to play several rounds to earn enough for another attempt, it will get frustrating. If you withstand the temptation until you've earned the cred for all the unlocks, you should have a pretty hefty bank to work from.
You see, coins and power-ups are a matter of diminishing returns. The amount of coins you can potentially earn from a song is less than you will spend to fully load yourself up. So, the more you use them, the more you're going to have to play in order to use more of them. A skilled player can profit earning Gold Stars with the use of power-ups on the first time a song is played (as coin awards are doubled on the first play), but even then it's still probably a better choice just to go for the relatively easy 4-5 stars that same player can likely earn without using any power-ups at all.
And don't forget about performing Goals in Rock Band World. These objectives pay out well and, in a lot of the easier cases, won't require you to use power-ups to get the scores you need.
The first commandment is to go forth and multiply
Score multipliers should be to you what children are to big tobacco; It's in your best interest to get to them as early as possible. It can be really hard to pull yourself away from rapidly scoring tracks but failing to drain out all lanes on your first checkpoint will be worse in the long term.
It's also important to know when to stop, as the value of increasing multipliers decreases the further you go into a song. By the time you hit about the mid-point of a stage, you should be looking to focus on the one or two tracks which feature the most activity, ignoring the others except to take advantage of white and purple notes. As often as not, just getting to the overdrive notes in a lane is enough to get another point or two of multiplier, so those are likely to still increase if you're diligent about picking those up. Which brings me to my next point.
They're shiny for a reason
You've paid for power-ups, so make sure you're using them effectively. Prioritize lanes which feature white (Overdrive) and purple (Note) gems on the horizon, ready to collect them. They may not always be positioned in the most convenient places (purple gems appear at random), but they are almost always worth the risk of collecting, even at the cost of Blitz Mode. The more opportunities you take to use your power-ups, the more valuable they become.
Not all lanes are created equal
The design of Blitz is such that it has to be possible to maximize each individual track's multiplier in the time between two checkpoints. This means that lanes which feature less notes in that space apply more value to those notes in terms of increasing multipliers, though the notes themselves still earn the same number of points as any other. This much becomes readily apparent after just a couple of games.
What you may not have observed is that the same applies to Overdrive notes as well. Overdrive earned on tracks with a low population of notes accumulates faster and more easily. This is most common on the Keyboard track, where a pair of hold notes can often completely fill your meter. Never, ever miss an Overdrive opportunity on a slow track in favor of another, denser patch of standard notes. You may even want to prioritize that low track over a heavier one in sections where all tracks feature Overdrive notes simultaneously, depending on the circumstances.
Finding a good balance
The selection of power-ups you take into a level can be the most significant decision you make in playing Rock Band Blitz. Power-ups come in three varieties, Overdrive, Note, and Track, but I prefer to think of them as existing in two categories for the purposes of planning a run through a song: active and passive. Active power-ups require participation on the part of the player after they have been activated, while passive ones carry out their functions without the need for attention.
For example, the Bandmate Overdrive power-up would be considered passive because, once activated, there's nothing else the player needs to do in order for points to be scored from the bonus as notes are automatically played in the selected lane. Runaway Notes, by contrast, necessitate that you hop from track to track along the route of transformed notes, thus should be classified as active.
Effective combinations of power-ups should have a balance between these two types in your Overdrive and Note selections. The pair I mentioned in the last paragraph works well, the Bandmate takes care of a track and, should a Runaway note come up, you're free to focus on capturing it (if the Bandmate doesn't manage to do it for you). Pairing Bandmate with Blast Notes, however, is asking for trouble as the automated player will inevitably hit a purple note, clearing all the other tracks and potentially ruining your rhythm.
Hitting the Jackpot
We can talk about various combinations of power-ups all day long but, in the end, I don't see a higher scoring option for the broadest range of tracks than Jackpot. Once activated, you cease scoring points, your earned score temporarily transferred to a pool and earning at triple the rate. If you make a single mistake in your playing before the Overdrive meter bleeds out completely, you get nothing, but if you don't screw it up, the score bonus is absolutely massive.
This is the power-up which separates the jungle cats from the domestic kittens, so to speak, and I tend to prefer it to the exception of all others. You need to be totally accurate in its use, employing it in sections which you know you can absolutely nail. There might be more potential for points available in the guitar solos of "Cult of Personality" than in any other single stretch of track the song has (and with no need to switch tracks), but that won't amount to a hill of beans if you try to Jackpot them and can't do it perfectly. Watch the spacing of notes carefully when you move to another lane and don't be afraid to let there be a half second where you're not playing a note in the interest of making a safe transition.
If we're following my general rules for balance, probably the best power-up to pair with Jackpot is Blast Notes, which will allow you to apply more focus to your most valuable tracks while still pumping up the multiplier on all others, and can in many cases make transitioning from one track to another without breaking your streak a little easier. That said, I don't rule out the value of Flame Notes as an alternative, which have incredibly high scoring potential, though they can be very difficult to keep up with.
Now, that's not to say you can't get a better score using other Overdrive power-ups. The simplest songs in the game (tracks with only two or three instruments) could be absolutely decimated using a combination of Bandmate and Pinball Notes. Speed metal songs which don't let up might be too difficult for Jackpot would work great with something like Road Rage. But, as an all-rounder (or if you can play perfectly), Jackpot is almost certainly the way to go.
Hold on for dear life
The last thing I want to point out is the value of hold notes, gems which give you additional points for keeping the button held down for the length of a trail leading away from the note. This is another one of those situations where your strategy may want to change midway through a song, as the points earned from holding notes feels far more significant later in a song than at its beginning, but my general tactic is to try and take advantage of sections with two hold notes over a faster combination of standard notes in a neighboring track when the situation arises.
Just as important as their scoring potential, they're easy to use, since all you really have to do to rack up their value is sit there. This makes hold notes an ideal way to take advantage of Jackpot because it's really hard to screw up and the point rewards can be massive. I've earned bonuses of as much as 100k this way with very little effort. And remember, holding Overdrive notes slowly (or in some cases, very quickly) fills your meter, so make sure you're always hitting those held white notes!
There you have it. This is how I've managed to earn the scores I have presently in Rock Band Blitz. These techniques don't all work for every song (or, at least, may not be the absolute best choice), but should be considerations whenever you're playing for score.
Now, go out there and kick my ass.