What is a good technique for remembering tones?
There is a technique I started to use and actually, I've seen it also in other dictionaries, so maybe I wasn't that original... 

But anyway, the answer is colors! When you're studying new Hanzi or vocabulary, just color each character according to the tone... It's very helpful to remember the tones, because after a while, you visualize the tones in your head through the colors. For example:



The tones obviously indicate the tones of the single characters1, it doesn't take into account the tone changes in spoken Mandarin2.

Obviously these tones are just mine, which means you can change the colors according to your taste. This technique is very useful for the computers, since you can use the colors. Concerning something handwritten, I can suggest using colored flashcards for each tone, for example, or using different pen colors.

For color blind people an alternative solution is needed. For single Hanzi on actual flashcards (not digital ones), a good idea would be the shape of the paper. Or the border style. For example an undulated border for the first tone and so on.

For expressions instead you could add a symbol below each Hanzi. I know that it sounds too complicated, but right now I don't have a better idea.



1: dictionary tones
2: tone sandhi