Don't expect to use tremendous weights initially. Your overall mobility will likely be the limiting factor, not your actual muscular strength. Depending on your hip and shoulder mobility, you may find as little as 10 or 20 pounds challenging enough to maintain good form. However, it's not uncommon for experienced lifters to perform good-looking reps with half of their bodyweight held overhead. The most important thing to remember is focusing on crisp, clean movements and never letting the weight get away from you during a repetition.