hi every one
how can I double my btc ??

You can't do anything magically with btc, you have to work for it just as for real money. Well you can double the btc pretty easly if you ask me, for example, you joina sig campaign and you get an amount for one post, then you post again and your btc are doubled (technically)

joke aside, it depends on the amount of btc you want to double and what skills can you offer.