Buying a first scope for a center-fire rifle is like a roller-coaster ride. You either get to the end feeling exhilarated, or feeling sick. Exhilarated because the scope does everythig beautifully, and you can't miss out to the maximum range, or sick because you invested so much time, money and effort, and it turns out the scope is not adequate for your purpose.

If you keep a few fundamental concepts clear in your mind throughout the process, your chance of getting what you need and it actually working the way you expect, is much improved.