You can promote other posts if you feel they deserve more attention and/or deserve a better payout.

All money goes to the account Hive account@null

This is probably open for debate, and you will probably get a variety of answers on this question. Personally I like it, although I did spend $6 promoting my last post, and only made $0.06 on the post itself... so I definitely lost money and will probably skip any future post promotion of my own unless I think my article is amazing.