Most refrigerator temperature settings are labeled 1-5 or 1-9, with freezers sometimes being labeled A-E. The best setting is usually somewhere in the middle. If it's labeled 1-5 try setting it on 3 first, if it's 1-9 than factory settings are normally at 4. If your settings are letters A-E than between B and C should be fine.
The best way to check is by sticking a thermometer in both the refrigerator and the freezer compartments. Your refrigerator should be below 40 F, ideally at 37 F. Your freezer should stay at zero. If middle settings seem too cold or too warm according to the thermometer than adjust the settings until you achieve the proper temperature. Allow 24 hours between each adjustment. These temperatures are important in that they prevent the growth of bacteria and keep your food from spoiling.
If your refrigerator and or freezer has been running at the appropriate temperature for some time and then starts to get warmer than it should be, you may adjust the temperature settings down to keep your food but contact an appliance repairman to assure there is not a problem with the refrigerator before it is not getting cold at all.
If your refrigerator or freezer seems too cold, first decide what seems to be too cold. If items are pushed to the back wall of the refrigerator they may get icy because they are placed closer to where the cold air is circulating in your refrigerator. If everything is too cold then, again, adjust the temperature to save your food but contact an appliance repairman to be sure there isn't a problem with your machine.
If your refrigerator is not cold enough but the freezer compartment seems fine, contact an appliance repairman. This is usually a tell tale sign of a defrost problem.
Also keep in mind the environment outside of the refrigerator. If you have a spare refrigerator in your garage it will not function properly if the outside temperature is lower than that of your machine. The same goes for excess heat outside of the refrigerator whether it's in the garage or in the house. There are kits that can be installed for refrigerators that are kept in the garage to avoid a problem with your appliance.