I buy liquid, either Tide or All brands (in the US), no dyes or perfumes. I find that Tide is slightly better than All, but in general the difference isn't a factor for me so I buy based on price. If I get something on my clothes, I have a pretreater that's pretty good. I use it rarely.
The amount of detergent they tell you to use is ridiculous. I use generally 1/3 of what they say, if that. If it's a very soiled load, I'll increase the amount of detergent.