If you've never bottomed before, I'd recommend you try some dildos on yourself first. Start with a smaller plug and then you can move on up. Find a position that works for you. Definitely lube up well. At least get used to the sensation first. Learn how to relax. This way, you'll be more prepared when you bottom with someone.
And every top is different. Some need to really go fast to keep their hard on, while others can take their time.