Google is your friend…
Based on the info in the links above–and your own eyesight–you can tell if your material is interlaced or not, and whether or not you need to deal with interlacing. If your DVD playing equipment is progressive scan [which a lot of equipment these days is], and your source material isn’t interlaced, you probably don’t need to do deinterlacing at any point.
If you use a TV tuner to capture broadcasts, depending on the hardware/software and settings, deinterlacing may be required
You can usually tell if you need to do anything, though. If there is no difference to your eyes, then don’t worry about it.