areaportals can cause leaks if they are not used and/or placed properly (see below). so check for leaks by trying to display the pointfile. if it loads up automatically then you have at least one leak; if it asks where the pointfile is stored, then you have no leaks. the pointfile draws a red line in your map that shows what is leaking from/through where.
similar to a normal leak, areaportals must seal off perfectly as well. if you have a leak with an areaportal, you will normally see the red line going from one face of the areaportal and circling around to the other side of the same areaportal.
in your areaportal's properties, you can control whether the areaportal is open or closed using I/O in-game (an areaportalwindow will open and close automatically based on distance, which you can set). I usually just leave them open all the time unless there is a good reason to close it. i use areaportals to seal off things like houses and apartments from the "outside world"...i place one inside each doorway, window, crack in the wall, exposed hole, chimney, etc that the indoor area has. that will *usually* make it easier to create visleaves and will also tend to improve frame rates.
PS: dont forget to check out the VDC, which is the perfect place for learning more about mapping and entities.
"Day breaks, but decay soon follows."
- Ava WinonaCurrently developing in radio silence... 99 BoltsHere's another project of mine... Assault on OverwatchAre you new to Source SDK? VDC