Steve has the right process here but some wrong materials!
First off, Sanding Sealer (A.K.A. Sand sealer, or sander sealer) is a base coat for varnish only!!! What he's trying to direct you to is called Stain Sealer or Stain Controler. This stuff is nessisary if you want an uniform color with pine wood. Also, do not use 220 grit sandpaper for first sanding. That fine a grit of sandpaper will close the pores of the pine and, between that and the stain sealer, the wood will not take any stain.
Here's my process for this type of project:
First, I clean the wood with Lacquer Thinner and a clean WHITE, lint free rag, then I follow with a saning with 120 or, at the very finest, 150 grit sandpaper. If you use sandpaper, you have to sand the whole thing or you will have areas that will take the stain differently. Take the time to clean the dust off with a Tack Cloth, the apply the Stain Controller. A Poly Brush works well for this. Allow to soak for a few minutes and wipe up the excess with a lint free rag. Apply the stain over the sealer before it gets a chance to dry, a poly brush works best here also. Wipe up excess with a lint free rag again. As Steve pointed out, every process should be with the grain of the wood. Allow the stain to dry for TWO days and then apply your finish, sanding thoroughly between each coat and cleaning the dust up with a tack cloth. Run your last coat through a "Cone Strainer", avaliable at your paint store. Use the fine one if you can get it. When your finish is fully dry (about 3 days) rub it down with ground pumice and a piece of wet felt. Clean off the white residue with a soft rag.
As far as latex VS. Oil, I vote for oil. Steve may differ on this point, but I have always found that oil finishes are tougher and resist scratches and water staining better.