D.B.
I think it's great that you want to do something for yourself! Start there!
I would not do up the make-up - you'll be in the sink and the water will get along the hair line and at least 1/2 inch in. If you want to take make-up with you to do afterwards, you can do that.
Some salons have you put something on (a smock) and others just put a cape on over you. I would wear something that buttons up the front, not something that you pull over your head, so that you don't mess up your hair putting it on at the end. Good hairdressers will make sure there are no loose hairs on your neck - between the cape and the little towel they put along your neck and under the cape, your should be okay. The blowdryer should take care of what's on your face. I usually wear a scoop neck shirt so it's not up high on my neck like a turtle neck or even a regular t-shirt. You can get a little bit chilly once your head is wet, so I would definitely wear something with sleeves.
If you see pictures of things in magazines that you think might be attractive, take them along. But not every cut is right for your type of hair. Tell the stylist up front, before you appointment, that you don't know what you're doing (!) and you need some time to talk before she grabs the scissors. Most stylists like this part of it! You don't need to know the names of things.
You DO need to let them know your routines - do you go to the gym 3 times a week and need something you can stick in a ponytail? Are you not so coordinated with a blowdryer and need something that is quick to style? Are you figuring you won't have a lot of time with a new baby? Do you have a strong feeling about short vs. long? What is the shape of your face (if you know)? What's your clothing style - jeans and t-shirts, sweats, tailored shirts with nice pants, etc.? Do you work, party, hike, swim - a lot? Do you have any talent or time to spend on your hair? Are you a complete klutz with a blowdryer? TELL THEM! Their job is to make you happy (so you will come back) and to give you something you can live with, while making you feel terrific and excited about your new look.
Tipping is 15% minimum, 20% customary - like waitresses. If you are going to the owner of a salon, and if he/she charges a higher price, then you don't tip. If, however, the owner charges the same as the other people, then you do. You actually have to ask - and they will tell you. If one of the less experienced people shampoos you or rinses out your color, then I usually give them a few bucks, up to $5, separate from what I give my main stylist - but I also cut back my stylist since she didn't do all the work herself. If you buy any products there (conditioner, etc.) you don't tip on the value of those. If you are unsure, ask the receptionist who is ringing you up what the cost is of the services themselves. Also, some people tip the person directly, but at larger, high-end salons, sometimes they have little envelopes you can leave the money in at the front desk. That's up to you.
You should ask friends for references - find people who have hairstyles you admire, and ask who they would recommend (and who they would NOT recommend.) If you have particularly difficult hair in some ways - extremely thick, or extremely curly and coarse, then I would ask people who have similar hair where they go (not just the salon, but the person too).
I think you should consider starting slowly since you are nervous - maybe just start with a good cut, and don't worry about highlights for now. You can do that at the next appointment if you want. Too many drastic changes can be stress-producing.
If you feel you are being pressured, tell the stylist to take it easy. Tell him/her you don't want to do anything too drastic the first time out. Don't feel pressured to buy all of their products. If you have a particular issue you want help with, you might want to buy a product that helps with that. For example, my hair is baby fine but I have a lot of it - I need help getting some volume at the roots so it doesn't lie flat. So I use a product for that. Someone with very coarse or damaged hair might want to use a good conditioner that they recommend. Once they look at your hair, they'll be able to give you some advice. Just don't feel that you need to walk out of there with a shopping bag full of professional products.
Again, their job is to make you want to come back there, so they should be working in partnership with you.
And don't be intimidated by the trendy pictures on the walls and in the magazines - they should be giving you a style that works for you and that doesn't require a professional to style it every day!