You have four options to consider. But before deciding on which options is best for you, you need to ask yourself one basic question - Are these modules going to be used together with other peoples' modules in a group or club set-up? If so, then you need to follow their standards. If not, then the next question is do you plan on taking the modules apart and setting them up from time to time or is the module construction method being used just a method to make construction easier and make moving the 'layout' easier at some time in the future when you might move?
The four options are
1. Use a connecting piece of track as others have described. This could be 9", 6" etc. The downside of this that it doesn't really look that good as retsignalmtr explained. I'll call this method the NMRA standard method.
2. Use a piece of connecting rail. As retsignalmtr discussed, you lay the roadbed and ties to the end of the module. Then you simply uses a piece of rail, usually 2" long, to connect from module to module. You need to undercut the ties at the end of the rail so the rail joiner will slide onto the ral without a problem, but it is easily done. When done correctly, it can be very difficult to find the connecting piece of rail, once painted and weathered. I'll call this the Free-mo method.
3. Lay the track completely to the end of the module and cut it flush with the end of the module. When modules are joined together there is no connector or railjoiner used and the rails simply line up with each other. Typically, the rail is soldered to either brass screws or PC boards ties or a PC plate so that the track gauge is maintained. This method can be tricky to do for a novice since the placement of the track must be EXACTLY perfect to have things line up and to prevent derailments. It does speed set-up time since no connecting pieces need to be installed.
4. Lay the track over the module joints and do nothing until it is time to take down the layout and move. Then you simple cut the rails at the joints and take it down.
The first thre are used for modular groups. I've used each method in various modular groups, each to a different level of satisfaction. The choice depends on how you want to use the modules, how much you want the connection hidden and how comfortabel you are with your skills.
