Angela from cyberspace (you really have to tell me where you are from when you write in, it helps me to know things about your climate, even about your soil) wants to seal her driveway but needs to fill up the cracks first. How to do it?
If we are talking about interlocking bricks, start by filling in the missing sand between blocks. Do this before sealing because you need to vibrate, or at least hammer on a block of wood, to compact the sand. You are better to batter the bricks before applying the sealer.
If we are talking about an asphalt driveway, there are asphalt driveway crack sealers on the market. However you may find that your crack appears to be a bottomless pit that just drinks up the crack filler. If the crack is wider than 1/8 of an inch or so, put in a foam tube called "backer rod". This is now available in various diameters at most weather-stripping counters. Just push it in with a screwdriver or putty knife. This goes about half an inch below the top of the driveway and allows you to use the proper quantity of crack sealer. Let the crack filler cure as per the packaging before applying the sealer over the whole driveway.
If you have access to an air compressor, and you may even want to rent one, blowing all the little dirt particles out of all the little holes with about 90 psi air pressure before applying the sealer will make your driveway sealer stick an extra season.
One of my radio listeners had the problem that a demolition dump bin had been set down and picked up from her asphalt driveway without protective boards -- leaving deep gouges in the asphalt. She is trying to get the contractor to fix it. In any case where you are working with an uncooperative contractor, document your problem: take photos with dates on them and get statements from any neighbours that might be witnesses to anything. This kind of homework on your part will usually push a contractor to act, and if you do end up in small claims court (never a good experience) you will have the proof that could make the judge decide in your favour.
If you decide to fix it yourself, you can purchase sacks of asphalt patching material. The video above. First, just as with the cracks above, clean it out well with a strong hose spray, a pressure washer or compressed air. Then use the crack sealer liquid asphalt like material to paint around the edge of the repair. This helps to get the patch to stick to the old surface and generally makes it much longer lasting. Then put in about an inch or two of patch material and pound it down with the end of a 2x4. It is rather amazing how much it compresses. Keep filling and compressing until you have it flush. A professional will use a hot asphalt mix and maybe even propane torches to make a longer lasting patch.