I know a lot of people know how to do this, but it may not be obvious to some of the new folk.
If you have any Steem or Steem Dollars then it is simple to transfer some of that to another user. There is no transactions fee for doing this, but be aware that transactions are public in the blockchain and will be visible on your Wallet page. You may want to do this to reward a good comment or post when your votes won't actually pay the author anything due to you not having much Steem Power.
Do do a transfer first make a note of the recipient's user name then go to your Wallet page and click either the Steem or Steem Dollars amount to get this menu:

That will give you this screen. Enter the recipient name and amount of either currency. The memo is just a note where you can say why you sent them the money, e.g. 'Thanks for your great comment on my post'. I don't know how long that can be. When you press the Transfer button you will be prompted for your password to confirm it.
Ideally we would have a Donate button on each profile to make this even easier. There is a Java 'bookmarklet' here that is supposed to do this, but it's not working right for me. It goes straight to the password prompt. I had a quick look at the code, but can't see what it's doing.
I hope this is useful to someone. You can test by sending me a small amount if you want and I'll send it back, perhaps with a little bonus. The smallest amount you can send is 0.001.
This is a 100% Steem Power post

Hi, thanks for sharing ... Iam new here so all the littel bits of information is helping to put the big picture together.
There are various articles that may help, but it can be hard to find it all. The site needs a good help page
I've used it before, I found it pretty straight forward, that's good for me as I find the whole site scary lol
Not sure I knew before that you can power up another user, i.e. send Steem to their Steem Power. There's an Advanced option on the Power Up screen to do this.