Unfortunately, I'm an expert on this.
For most guys this will be the only experience they get with TS girls so enjoy and try to have fun. If you get lucky you might make a new friend (outside of being a client), maybe even a friend with benefits.
I would say on your first time just look for the girl you like the most and don't worry about price, I'd imagine that if you have a bad experience you might reconsider trying again. I wouldn't say it's your first time because some girls try to take advantage of that, you won't necessarily know what to expect so they have the advantage. I got taken advantage of... So don't repeat that mistake. You should expect to go all the way, anything else is not normal.
I don't know what you are into sexually, but keep in mind that all girls don't like the same things so if she doesn't want you touching down there you're better off not bothering. One thing you should know before you decide to see someone is whether they are only a top or only a bottom. If this is incompatible with your stance you might get fucked, literally. LOL. Nah, not like that, but some girls will want you to pay up front then try to pull some bullshit, especially if you live in a big city. Reputation with clients isn't as important as it is in a smaller area.
Just a warning, if you have an addictive personality type, you'd be better off staying away unless you have the budget for it.
Good luck man!