How to torque a bolt

To properly torque a bolt/nut the following must be done;

Make sure all threads are clean and is the right fastener for the part. Right thread pitch, length and diameter.
Lubricate the threads with a suitable lubricant, if necessary.
Consult the manufacturer's fastener tighting chart whenever possible (all threaded fasteners have different torque values based on bolt/nut grade, size, tread pitch, material and if lubed or dry).
Bolts of different sizes are torqued in different steps. Smaller diameter bolts are generally torqued in one step. Larger bolts are generally torqued in 3 stages. 1/3 of the torque spec, 2/3 of the torque, then full torque. For example, if cylinder head bolts are supposed to be torqued to 90 foot-lbs, then they would be torqued first to 30, then to 60, and finally to 90.
All bolts/nuts should be snug or finger tight before torquing. This will ensure the proper torque requirements are met.

Should you re-torque a fastener, you must first loosen it, then completely torque it.

Here's a link to fastener sizes and torque values that may be helpful to you..... http://www.derose.net/steve/resources/engtables/bolts.html