First, a word about nails. If there wasn't a nail there to begin with, don't put one there. Chances are the person who made the chair or table knew what they were doing and didn't plan on someone else driving a nail through the joint to make it better. Nails have a purpose, and it's not furniture repair under most circumstances.
More nails will not solve the problem, but more than likely damage the wood and create an unsightly mess.
I could say the same thing about staples. While it may seem smart to use a staple to keep a cracked joint together, it's a big no-no. Not only does it look bad, but over time it will pull apart. Often staples will split wood, too. Don't use staples. They're fine for holding in upholstery (sometimes), but otherwise they have no business in furniture repair.
Staples are a lazy repair that look bad and function poorly.
Glue is the woodworker's choice for keeping joints together, and different glues are used for different purposes. Some joints can be repaired using conventional carpenter's glue, but others should not. If you're not sure, don't slop a random glue in there and assume that it's going to hold correctly. One thing I encounter a lot is a joint where someone has dumped in an enormous amount of industrial epoxy. Yes, it holds. And holds. And holds. It makes disassembly a major chore for the restorer and can often result in damage to the piece. For many antiques, hide glue is the glue of choice for the restorer. It allows a long open assmebly time, holds strong, and is easily dissolved with little effort should the piece need repair later. If you do choose the appropriate glue, apply it correctly and wipe off any excess. Hot glue guns are not for funiture repairs. It may be quick and easy, but don't do it.
The wrong glue and too much of it.
Now a word about wood filler. It seems like a great idea to fill a crack or damaged area with wood filler, and that's indeed what it's for. But - you wouldn't believe how this simple material can create such ugliness. And - not all fillers are created equal. The wood filler a painter may prefer is generally not the wood filler a woodworker will use. If you're going to use filler, use quality material. Many fillers can be purchased pre-tinted in many colors and then sanded and blended in. Please, do not dump filler in, smooth it over with your finger and then leave it. Take the time to sand and finish properly. The results are worth it. Also - never use caulk as wood filler. I encounter this all too often.
This filler might have been effective if applied correctly.
Now, of course, this isn't an exhaustive list what you shouldn't do if you're going to repair your own furniture. It's always best to consult a professional, but I understand as well as anyone the desire to do it yourself. To insure that your repair lasts (and to make it easier for the next person who has to fix it), take the time to do it right or take it to someone who will. Don't drive a nail into your antique table. Don't screw a metal bracket into your grandmother's chair because it's getting weak joints. It's the wrong thing to do. Please... respect your furniture.
Today I pulled 38 staples out of a table leg and spent another half hour chipping out caulk and epoxy. This was after pulling out 14 nails. Guess how much of that was there originally? None of it! And none of it is there now. And it's strong and beautiful once again.
