How to ask for a raise?

How to ask for a raise in this particular situation?

• I clean houses for a living, and although I like doing my best to please my clients, I still feel "used" sometimes. Sometimes they'll ask for extra things, like cleaning the oven, fridge, etc, I mean these things usually take a long time, and I do charge to do them, but for some people, they seem to "forget" that detail and still ask for me to do them and leave no extra money. Also, I've been cleaning for the same clients for a very long time, I have never asked to raise the price, but I feel it's time for me to ask to raise the price a little bit. How do I talk to them or leave a letter/note about the raise and about charging the extra things without being rude? Thanks in advance! ;)

• Answer:

  i think you should leave a letter. i feel like it would be awkward to ask in person since its not like your 'boss' . still no comments huh. sry mines not that helpful