As others have stated application is important, but I'm going to assume since you're asking in a Precision Forum that most of your shooting will be at paper/steel at 100-1000 M. The best advice I can provide is get what you can afford...well, duhh, but wait, hear me out.
If you can afford an S&B, outstanding, and that's the price range you should be considering. That's not to say you have to pay that kind of cash, half as much will still get you an outstanding optic. Anything less than top of the line, now things can get a bit confusing courtesy of Fan Boys and Marketing. I've had a few "garbage" scopes over the years, and some were just that, others were perfectly serviceable assuming you could ignore the odd shortcoming. I have a few friends with Vortex Diamondbacks, and I've had a few Cabela's Covenant scopes. Both seem to do the job adequately, so if money IS an object you can get something serviceable for under $500. I'm currently using a Cabela's Covenant 5, 5-25 X 56mm. To be blunt I think it's likely I'll be trying to get them to honor that lifetime warranty listed on the side of the box one day. Regardless it works, it tracks properly, it's acceptably bright at full power, my only complaint is the eye relief is a bit weird as you move through the power range. In the end get the best you can afford, if you can afford $1k, it's a safe bet you'll be happier with a scope that was in the $750-$1000 range then my Covenant 5. If you have to go lower end a Vortex is a good bet, and the warranty is nice, the cheaper the scope the more likely you are to need a good warranty. Once you know what your going to spend, it's down to power range, reticle, and Mil/MOA. Power range/size 4-16 X 44 to 6-24 X 50 will likely fit your requirements (you'll want a 30mm tube most likely). Reticle can be simple or "busy" look at a few, some of the more elaborate may be a bit distracting (I like them some don't). Mils/MOA the turrets and reticle need to match as others have mentioned, look at the math required for both, figure out which you do in your head better and pick that one...Mils for me.
Most important is take a trip to a local store with a good selection so you can see the features first hand, and also compare a few side by side.