is when I don't have exact change, and I just round up to the nearest bill I have if it's not too crazy. The girls make a lot of money per hour, more than most people. Where I live tipping is not the norm, but it may be different in other parts of the country.

I never tip, but I take gifts, some candles and a VS gift card.  They always love them.

Swim

I don't believe we have to. I do if she is very good or does something special. I also tip when I expect to see them again.

It will be obvious.....

when you just can't help yourself but to give her a bonus... then you should tip.  

It really will be obvious.  I have only done it once and when I did it was in the 50% range.  But she deserved very bit of it for time, service, and attitude.

you are never expected to tip and as previously stated it is always appreciated.

What we appreciate is polite gentlemen who have good hygiene and thats about it.

I ALWAYS tip at the AMPS. Their "take" is lower then most agencies. Unless I get a sub par performer, I will tip them as a general rule.
I will also tip any provider that goes above and beyond the call of duty such as extra services and extra time.
I tip some agency providers, but not all.
I rarely tip indies unless there is something extra on the table.

The best tip you can give a provider is repeat business.

At least here, in the US, tipping in restaurants is culturally mandatory, so to speak.

With decent provides, it's all included. The tip is extra appreciation.

What are some (not all reasons) good times to tip?

- You went over time, and especially if you go over and she is working her ass off (so to speak) for that extra "cup of coffee"
- She really did go the extra mile for you in a way that you appreciate
- You thought the service was worth more than asked
- You really liked her and plan to see her again... building good will with a lady makes for fun times

If I've seen the lady before and have always gotten good service, I put a tip in with the donation and give it to her at the start.

Did you get extra time and/or services perhaps?

If the answer is yes, karma would argue that you should leave a tip.