There are a couple of basic styles of scope mounts, and several manufacurers make them.

Probably the most common around here is the "Leupold" style. The base has a fixed front dovetail, that the ring twists into, and a rear windage adjustable ring mount, with a mounting screw on each side. Leupold, Nikon, Burris, Millet, and probably a few others make this style. They are always made of steel, and can be had in a 1-pc or 2-pc base. A 2-pc base will save you some weight and give you more clearance to the loading port on your bolt action. Others claim the 1-pc base adds rigidity to the action. I have drifted away from using this style in recent years. Sometimes the rings can be a pain to line up, and I've had the windage screws come loose on me during a hunt.

The other popular style is the "Weaver" style. Many companies make Weaver style bases and rings, and they can be had in aluminum or steel, if weight is a concern. There are some quick release style rings that return to zero when you remove and replace the scope. This is a nice feature, if you plan to have iron sights as a back up to your scope. I have Warne Maxima bases and Quick Release rings on my .375 H&H. They work well, and as advertised, they do return to zero.

My favorite scope mounts are the Talley Lightweights. They are a mounting system where the base and ring are one integral unit. The rings line up perfectly everytime, and they are lightweight and easy to install. I have recently changed most of my "Leupold" style mounts over to the Talleys. No more loose windage screws for me.

Personally, I would avoid the over/under mounts (the ones where you can use your iron sights or a scope). They are not very sturdy and picking your head up to look through the scope of a high-powered rifle is just asking for trouble.

No matter which option you decide to go with, I recommend mounting your scope as low as possible. Most scopes, with a 40mm or smaller objective, can be mounted in "low" rings without issue.

Good luck!