Sometimes you don't need a frame, if you buy a painting on a stretched canvas. A quality wooden stretcher can be hanged without a frame, it really depends on your taste. However, if you decide to frame it, it's best to not do it yourself - bring your painting to a framer.
Some people also choose to put a UV glass protection on the painting, but it's not necessary (unless your painting is exposed to direct sunlight, which it shouldn't). Generally, oil paintings should not stay under glass - they should "breathe"; with high humidity it's especially important - there's a risk of mildew.
So, nice frame or no frame - use reasonably strong hardware, some frames can be really heavy. Avoid taking the canvas off the stretcher - each time a painting is taken off and re-stretched again, colour layer gets damaged. Give it to a professional, if it's that necessary.
Don't hang your painting close to heating devices, cooling devices and whatnot. Avoid high humidity locations like bathroom, and direct sunlight.
As any other thing in the house, painting gets covered with dust overtime. A thick layer of dust can lead to cracks and peels. The right way to dust a painting is with DRY and CLEAN light synthetic brush. Feather dusters can leave stuff that sticks to the painting. DO NOT USE wet cloth for dusting, even if it's just water. Same goes for detergents and cleaning products. Every now and then check the back of the painting, make sure there's no mildew. Dust your painting about 3-4 times a year at most.
To replace a painting, avoid holding it with one hand over the top - take it carefully with two hands on the sides. Hold it on the stretcher, don't touch the colour layer with your fingers. If you need to pack it, do not bubble wrap it - put a layer of clean firm cardboard (or similar material) over the front and back of the painting, then you can bubble wrap it over. Secure the angles of the stretcher with some extra protection. Keep the painting upright, not horizontal.
If your painting got damaged in any way and you want to save it, please contact a trustworthy professional to help you.
Enjoy your art and come for more :)