The primary answer here is speed , but there's more to it than that.
Keep your speed up, making matches, so you'll continue to receive an ever increasing speed bonus.
Your goal here is to get to the x1000 speed bonus where every match creates an explosion (and the gems flash) - but any speed is better than no speed at all.
Make matches from the bottom up, there's more chance of a cascade Be aware of the multiplier gems - a match has to cause a cascade that removes 12 tiles (and more than 10s apart from the previous multiplier gem).
So, make those cascades and grab the multiplier gems early.
Don't plan out your next move too much.
This is Blitz, remember?
60s is not enough time to ponder the inner-workings of cascades.
Do look for more matches ASAP.
That is, as soon as you locate a match and begin to drag it, start to look for the next.
Remember that you have a Hint button - but that it takes a few seconds to locate, move to it, and click.
Do purchase power-ups.
With one of the latest updates, you can purchase powerups like multipliers in the field as you start, gem-swappers, and extra time.
In my personal experience, the gem-swapping and extra-time are the most valuable to my score.
If/when you do create a 5-in-a-row match and obtain a HyperCube, you should use it ASAP, on the color that you see the most of.
This should create many cascades, up your speed bonus, and with fewer colors on the map, it should be easier to create your next match.
(Remember that 5-in-a-row is the most valuable, so don't waste the opportunity on anything else).
Don't forget that if you really want to be a bejeweled-blitz-master, you'll need to do the following: Practice practice practice Watch
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I've played on facebook and my high score is ~1.2 million.
Besides speed, the major factor contributing to super high score is the multiplier.
A 8X multiplier at end game means you'll get 8X more score, which is more feasible physically than playing 8X as fast.
Luck plays a big part too, I could play a perfect game with a couple blazing speeds runs but end up with low score because I didn't get many multipliers.
However speed is the one thing you have almost complete control over.
So go for very fast speed and make sure you clear those multiplier when you see them.
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Speed it is mate.
Try to go faster then the diamonds are destroyed and of course look out for 4 or 5 in a row which you give you bonuses where you can rest your eyes for a few seconds.
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I Played on iPhone and my highest score is 698K.
There is no tactics but your speed, you need to look all across the screen to get the possible either 3, 4 or 5 of a same kind.
Enjoy playing guys!!!
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I've played Bejeweled Blitz on Facebook and my highest score is ~230k.
I've only gotten above 200k a handful of times and notice a definite trend for most games to just not add up.
I think I have about 170 games in the 25k bar –
this version of the game tracks these stats for you.
The strategy that has worked the best for me is working from the bottom up, switching from left to right.
Working bottom up allows for cascades without disrupting your flow, and similarly for left-right letting you plan in advance and then move while blocks are falling elsewhere.
The cascades are important because you need to destroy 12 tiles at once to drop a multiplier, and those are key to a high score.
The speed bonus does help, but let it come instead of forcing it, as it doesn't compare to multipliers.
Many rounds just won't pan out, and you'll have to be patient to get the exact right factors for a high score (this appears generally true from all my friends' scores too, where their totals in 25k, 50k, 75k, etc.
categories match my distribution).
If you're not enjoying each game much, it probably isn't for you (it's not for me), because high scoring games are going to be relatively rare for some time.
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I average a score of ~60,000 on Bejeweled Blitz for iPhone, yet I see a lot of my friends posting scores of over 250,000.  Are there any tactics for achieving such a high score, or is it really just down to finger speed, and/or luck?
Are there any tactics for Bejeweled Blitz?
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The primary answer is speed. Working bottom up allows cascades that won't disrupt your speed. Keep your speed up, making matches, so you'll continue to receive an ever increasing speed bonus and make sure you clear those multiplier when you see them. Try to go faster then the diamonds are destroyed and of course look out for 4 or 5 in a row which you give you bonuses where you can rest your eyes for a few seconds. Besides speed, the major factor contributing to super high score is the multiplier. Working bottom up allows for cascades without disrupting your flow, and similarly for left-right letting you plan in advance and then move while blocks are falling elsewhere.  Remember that you have a Hint button, but that it takes a few seconds to locate, move to it, and click.  Gem-swapping and extra-time really valuable.  The cascades are also important because you need to destroy 12 tiles at once to drop a multiplier, and those are key to a high score.  
Keep your speed up, making matches, so you'll continue to receive an ever increasing speed bonus and make sure you clear those multiplier when you see them. Try to go faster then the diamonds are destroyed and of course look out for 4 or 5 in a row which you give you bonuses where you can rest your eyes for a few seconds. Working bottom up allows for cascades without disrupting your flow, and similarly for left-right letting you plan in advance and then move while blocks are falling elsewhere.   Remember that you have a Hint button, but that it takes a few seconds to locate, move to it, and click.   Gem-swapping and extra-time really valuable.   Besides speed, the major factor contributing to super high score is the multiplier. The cascades are important because you need to destroy 12 tiles at once to drop a multiplier, and those are key to a high score.  