shepheard: May I say Welcome to the forum, in case no one else has.
The info above is very good. However, I wish to clarify another issue. Quite a few of the newer reloaders have been posting that they selected a certain load (usually mid range to upper range), assembled several of them and up to a box of cartridges, then gone to the range and tried them. Some have experienced problems with over pressure loads by doing this. Please be safe.
Please follow the suggested "working up a load" method of selecting the starting load, loading 5 for rifle and up to 10 of them for pistol, keeping them well identified and seperate from other loads; then loading another 5 to 10 cartridges with 0.5 grain increment for rifle, and usually a 0.3 grain increment for pistol; keep increasing the load until you get to the max load, never over max.
At the range you should be shooting each seperate load at well marked targets that identify the load shot and that load only. Watch for pressure signs with each shot as you go. You can then sit down and see trends to and away from accuracy. Then go home and load accordingly or for more testing.
Good Shooting!