What are you going to do with the disks?
This model records to DVD+R or DVD-R. These are permanent recordings and can not be recorded over. They are very compatable with other DVD players and the cheapest type. DVD-R will need to be finalized to work on other players and DVD+R probably will not need to be finalized.
It also records to DVD-RW. The advantage is that you can erase these disks and use them again. On this model, you can not do much or any editing. These are also compatable with other players if you record in video mode, but not so compatable if you use VR mode. They can be re-recorded maybe 1000 times. These cost a little more than the R's
Thae last type is DVD-RAM. This is also a reusable disk and this is where you get all your editing features. The bad thing is that they will not play on most DVD players, so consider it as a VHS tape for your own use. They can be re-recorded maybe 100,000 times. It is the most expensive disk.
Like the other post said. Use quality brands (read NOT Memorex) and use the 2 hour mode for your movies unless they are too long and then use the next longer mode to make it fit. The 6 hour mode is as bad or worse than the 6 hour VHS tapes. Disks are cheap. Do not waste the quality of your DVD recorder by trying to squeeze more on a disk, that defeats the advantage of a DVD recorder over VHS.