Cutting and Dry Run-
Step 1: Everything must be truly dry. There are some glues that resist issues with moist areas but course of wisdom is Dry, Dry, Dry.
Step 2: Cut and dry run your fittings, pipe, and components. Typically you don't want to insert fully because most parts are tapered so its easy to get your parts stuck together. But planning out how it all will go together is critical.
Primer and Glue-
Step 3: We prefer a medium, clear primer glue because it just looks better and the medium body fills most voids. Sometimes a heavy body glue is best but normally a medium body works. Downside is medium body normally "sets" faster so you don't get a lot of fudge time.
Step 4: Primer. You must prime both surfaces that are coming together. So its the outside of one surface and inside of the other. Primer both cleans the pipes and softens it. Normally priming can be done any short time before the gluing.
Step 5: Gluing. Several points to remember. First, like priming both surfaces have to be well covered with glue. Second is glue sets quickly... seconds. So you have primed, now coat both surfaces with glue and slide together with a slight twist. Hold couple seconds; done. The meld between the 2 surfaces will normally be stronger that the pipes themselves. This is why pvc primer/glue is so popular. Although the glue sets quickly, you should wait 24hrs for the glue to fully cure.
Step 6: Parts. Most often you are rebuilding glue joint to part to part to part.... So you simply have to be systematic. Many times you are working toward a flex pipe with a little give so you work toward that and the last is into flex pipe. We also have some "cheats" in the PVC section that can help.
Step 7: GOOF- If you see quickly you goof, pull the joint apart and immediately reprime the two surfaces. The primer will remove the glue so lather on to remove the glue.
a. Since starting in 1995 I was trained after all the gluing is done, lather on a second coating around the outside of the joints as added protection for a good glue job. I'm thinking this is probably not necessary since its not done when originally doing but why not? I only have had a couple glue jobs fail so I still do this.
b. How much overlap on surface to surface do you need. My rule of thumb has always been at least 1/2 of the available contact space. On most pvc fittings there is a graduated reduction as the pipe slides into the fitting. Getting at least 1/2 together has always been sufficant but full fitting is best. I literally will mark the spot on the inside pipe/part to confirm that I reached that point.