how do you know who tipped you?

[Unregistered]

how do you know you left you a tip?

[Unregistered]

In the lower left-hand corner of your screen is a Main Menu tab. Tap it and in there are a few options, one of which is "messages". Tap that and under "news feed" you will find who tipped you. The only catch is that it only holds a certain number. If you don't come back for a while, the older ones will have been deleted. The other tab in messages is "wall" where people can leave you a message if they cleaned. As far as I can tell, this one keeps messages a long time. Not everyone leaves a message, however.
I hope this helps!