Ok, the first and most important thing to do is, make sure there is no power on the wires you are dealing with. Check it with your meter to be sure. It is also a good idea to check your meter on a circuit that you know is hot(to verify it is working properly). When you finish your basement or finish that garage off you will be happy that you put that 3-way switch in instead of a single switch.
To get started you have to have one of the switches and your ohm meter. Make sure the meter is set to ohms. It may just have a symbol that looks like a fat horseshoe to mark ohms. You need to find the common lead(screw). The common is sometimes but not always indicated by a different color screw. Take your meter and touch one lead to one screw and the other lead to another screw. If your reading changes from OL to a small number like, 0.1 to 3.0 you have a circuit. Then with the meter leads on the same screws flip the switch and make sure the meter changes to OL. Knowing this you need to find the 2 screws that have no circuit between them(no matter the position of the switch you always read (OL) or no circuit (–) with the meter). The 2 screws with no circuit possible are the travelers. The other screw is the common and will be the one connected to your power on one switch and it will be the one taking power to the light(s) on the other switch.
Lets go over what we know so far:
1) Turn the power off
2) Find the common screw on both switches
3) Find the 2 traveler screws on both switches
4) Determine what switch receives power
5) Determine what switch feeds power to the light(s)
Now your ready to install. Plain and simple 2 wires that are connected to nothing else must run from the 2 traveler screws on on switch to the 2 traveler screws on the other switch. Please make sure if your using a piece of romex wire for travelers you put black tape on the end of the white wire at both switches. This lets you know power may be present. All that is left is to connect the power to the common on one switch and the power going to the light(s) on the other switch.
In the switch box feeding the light(s) the neutral will be capped off. In the switch box receiving power the neutral will be connected only to the neutral going to the light(s). Make sure that the white wire(neutral) that is with the black wire feeding power to the switch is connected to the light(s). The light or lights in the circuit will be the only place the neutral is used.
There you have it. Yes it really is that simple.