Blue loc-tite.
Since it's a safe bet that your scope isn't sighted in right now, buy two things from the hardware store. First, a small bottle of naptha. Second, a bottle of BLUE loc-tite. The red stuff is forever, the blue can be broke loose with tools and effort.
Take the scope and mount completely off. Remove the scope from the rings, also.
Clean everything. Reciever, scope tube, bottom and inside of rings, mounting base. Use the naptha for this. Takes off the gunk and won't leave a residue. If you can't find a small bottle of naptha, Zippo lighter fluid works, also.
Check your screws. If they are buggered up in any way, throw them away and replace them.
Make sure you have a properly fitting screwdriver or allen key. Most scope rings are allen heads, most bases are slotted. The slotted screwdriver from your toolbox will not fit properly. Firearm screws are not tapered, the driver from your box is. Spend 12 bucks and get the B-Square set from any of the local sporting goods or "big box" stores around you.
With everything cleaned, proper tools and the loc-tite in front of you, mount things in this order:
1) base. Put loc-tite on the screw threads and finger tight all screws. Driver tight all screws, starting from the center and working out. There should be four screws, two front, two back. When they're all tight, tighten them again. As tight as you can get without stripping them. Be sure to push down on the driver while turning it.
2) rings. Lay the scope in the bottom halves, to see where the rings need to go for proper eye relief. Set the scope aside again, remove the screws from the rings (the ones that go horizontal) and loc-tite them. Tighten same as step one.
3) scope and top halves. Put the rifle in a padded vise, pointing toward a doorway or with a string hanging in front of it. The string is better, your doorway might not be square. Put a level across the base, rotate the rifle until it is level. Lay the scope in the bases, tighten the top halves WITHOUT loc-tite. Seeing the string hanging down through the scope, turn the scope tube so the vertical crosshair is aligned with it. Your rifle and scope are now level. One screw at a time, remove, loc-tite and re-tighten them. Let the rifle sit for a few hours before firing.