DVD player keeps saying loading, not playing DVD movie, what should I do?

It probably won't play but one thing I do is wash the recorded part with mild dish soap and water when I see a spot or spots on it. If you have a computer with a DVD player you could try it on a computer which might tell you what is wrong. 

The disc itself could be bad. wrong region, poor copy, or just the movie itself is scrambling the player.

Try removing the top cover and with a fiber cloth spray little eyeglass cleaner on it and gently wipe the eye of player located under disk tray. Also clean tray in case any dust on it. If dont work it may be disk needs cleaned or has scratches on them

Try blowing canned air into it but make sure you don't spray the fluid and have the deck unplugged.  Or, get it cleaned or buy a new deck.

Often when a disc skips I check and it has a hair on it.

Get it fixed.....................

Replace it. Go t a BluRay player, as that will give you more bang for the bucks.