You know, I see lots of findom tip threads for new Dommes, but not much for subs, by subs, so I’m going to give it a try.
1) Research before your first send. Research the fetish and the community, and the particular Domme. Her basic info should be easy to find from Her profile.

2) Learn about payment methods. Which ones are more anonymous, if that matters to you. Which are more stable. Which are more SW friendly. Which keep a cut of the money you send.

3) Know what you want before you send. Is this a one off send? Are you looking for a little play at the moment? Are you looking for a longer term arrangement or even to work towards ownership? Knowing what you want and sending intentionally with that goal in mind helps.

4) If She has a published minimum, send a tiny bit more. It’s amazing how much 5 bucks over a posted minimum can help you stand out. If She doesn’t have a published minimum, look and see what tributes She posts to see what Her ballpark expectation is.

5) With that said, don’t go so overboard with early sends that you’re setting a precedent you can’t keep up. It’s easier to work up to bigger sends than to work down because you blew your savings trying to make an initial impression. You want to look good, not overwhelming.

6) Being pleasant to deal with matters. Allow yourself to be intelligent, funny, or charming, if you are those things. She’ll still use you, but She and you will both enjoy it more.

7) Finally, this should be fun for both parties. Don’t internalize the role play so thoroughly that this actually makes you miserable.