You will want to wear goggles to protect your eyes and a mask so you don't inhale the sawdust. There's nothing worse than getting sawdust in your eyes or up your nose! Also, make sure you have plenty of extension cord to allow you to move around your project as you sand. It's a real pain in the neck when your sander comes unplugged because your cord won't reach! @#$%*!
Being such a frugal gal, I still struggle with this one. DO NOT skimp on sandpaper, change it out frequently, especially when you are removing years worth of stain or paint. It is worth the small extra cost for the time it will save and the end result. If the project you are working on needs a lot removed in order to get down to the bare wood, start with a coarse grit sandpaper. I usually start with 60 grit. Make sure you move the sander with the grain of the wood, not across the grain. Once I get most of the old finish off, I switch to 80 or 100 grit, which is for smoothing out and leveling most surface blemishes. Then for a smooth surface that will be ready to finish, I switch to 220 grit.
Once it is sanded down you will need to clean the surface well with a tack cloth, which you can get at Lowes, Home Depot, or any store that sells paint supplies. I usually use an old t-shirt that I have ripped into smaller pieces, then dampen it with mineral spirits and wipe over the surface to remove all of the dust. Once it is clean and dry you are ready to stain.
You may want to test the stain color in an inconspicuous area just to make sure it is the color you want. Stain colors don't always look the same on different types of wood, so it may not turn out exactly like the color sample you picked out at the store.
If you choose to stain your project indoor, make sure to open windows and turn on a fan to help with ventilation. Never stain or use polyurethane near an open flame or pilot light. To apply stain, I prefer to use a cloth (old ripped up t-shirts), but many people use a foam or paintbrush to apply it. You will want to wear gloves to protect your hands, otherwise, your hands and fingernails will be unsightly for days and days, because nothing seems to remove it! Even with gloves the stain sometimes seeps through. When I remember to put some vaseline on my hands before I put on my gloves it seems to help.
Apply the stain liberally, working in small areas as you go. Rub it on well to make sure there are no drips or runs, and then once the surface you're working on has been covered with stain, go over it again with a clean cloth to remove any excess. Let it dry completely in a well-ventilated area. Lightly sand with a fine sandpaper, like 220 grit, and wipe with a tack cloth before applying the next coat. Usually, 2-3 coats are all that is needed.
Now you are ready for polyurethane or any other type of coating that will provide protection for the wood surface. How the item is going to be used will determine the type of product that will be best suited for your needs. If it is a dining table, a stronger finish is desirable, so polyurethane is always a good choice. I like to apply poly with a foam brush because it goes on so smoothly. If you put the foam brush inside a plastic baggie and put it in the fridge while the first coat is drying it will keep the brush fresh and ready to use for the second coat. This also works well for paint brushes and rollers even! After the first coat is completely dry, lightly hand sand with fine grit sandpaper. Clean the surface of all dust before applying the second coat. Usually, two coats of poly will be sufficient.
Lastly, make sure to check the weather forecast before you plan a project like this because the stain and poly will not dry properly when it is humid.