Not getting relaxed

Helen • Your average 19 year old college student
I've had sex before with one person, but I always noticed that when I did I was really really tight in the beginning and it hurt a lot. Apparently that is caused by not being turned enough/not being relaxed. My current boyfriend and I plan on having sex soon so I was wondering if there were tips for helping to relax before hand so the beginning of sex isn't so painful.