how do you get biased samples from a fair coin? (say, 0.3)

(this one has less wow, i guess)

1. You take a string of fair samples 0101011101010 2. you split it into chunks of 3 (8 possibilities, so each one is 0.125 chance) 3. 000, 001, 010 -> 1, and all the rest is 0, which will get 0.275 chance

Any better approaches?