Sawdust build-up can create heat and friction when you use a hole saw. One solution is to drill a smaller hole inside the area to be cut out that will allow the sawdust to escape. Size the relief hole according to the size of the larger hole. If, for example, you are cutting a 3-in. hole, drill a 1-in. relief hole. Don't drill the hole too close to the center, which you need for the saw's pilot bit.
Glue will soak more into the end grain of wood and can potentially result in starved glue joints. To help prevent this, you can “size” any end grain to be glued with a mixture of glue diluted with water. Dilute just so that when it is applied, glue drops don’t form at the lower edges of the wood. Another method, somewhat less effective, is to coat the end grain with full-strength glue, allow it to dry 5 to 10 minutes, then re-coat with glue and assemble.