If you paint , sooner or later you'll probably paint something which you'd like to frame and it's good to know the options available.
For watercolour it's usual to frame under glass to protect the painting from damage. You can use a single mat (bottom right) or a double (bottom middle) which makes it a bit more "3D". I've also been playing with floating the paintings (bottom left) where a deckled edge floats over the mat - looks great for landscape paintings.
While I usually use a plain white or black frame I'm currently trying a delicious red one . Plainer profile mouldings seem to suit watercolour , maybe keep the ornate frames for your oil or acrylic.
Mats are usually best white - and shouldn't be lighter than the white parts of your painting (this really makes your work sparkle).
Framing style is a personal choice but always make sure that your framer is using acid free archival materials, so that you don't end up with foxing (those nasty brown dots which can appear on the backs of old paintings).
So, once you've finished your painting , spend some time thinking about presentation , and what will give it the wow factor!