Learn how to replace your stick's tip with glue, a little knife work and sandpaper.
1) Remove the old tip by cutting it off with a Stanley knife or utility knife and as close to the ferrule as possible. Do not under any circumstances slice into the ferrule or wood of your cue' shaft.
2) Next, scrape the surface clean where the old tip was glued by using the edge of your knife.
3) Take a little piece of 150 or 180 grit sandpaper (very fine/very small grit size) and press it tightly against the surface where the tip was just removed. Hold the sandpaper firmly against the top of the ferrule there while spinning the cue around to sand the surface until you're sure it is completely level, flush and smooth.
4) Take a piece of 400 grit sandpaper, lie it flat on a smooth, flat surface facing upward to sand the bottom of the new tip, again with a circular motion and again until this surface is likewise utterly flush and smooth.
5) Check for a future flush connection between tip and cue stick next. Hold your new, sanded tip and press it against the ferrule. Turn the cue and tip around its whole circumference in front of a strong light source to check for gaps between the two. If you find any gaps at all, re-sand both components as in #'s 3 and 4.
6) When you are satisfied that you have one continuous surface between tip and stick, place a small drop of glue on the surface of the ferrule you've have just sanded. Add a very small drop of glue onto the tip, too, at its bottom. Smooth the glue along the surface a bit with a toothpick's edge.
7) Place the tip carefully and of course, as centered as possible to create a flush surface, so the glue drops come together (use only a little glue so excess doesn't spill over the sides. (Small amounts of glue might squeeze out the sides. This is normal, as long as you don't have glue all over the place you cannot remove immediately after for a clean ferrule.)
8) Press down hard on the tip. Don't move it off the center of the ferrule, however. Take a rubber band, loop it around the cue shaft about six inches inches below the tip several times and pull one end over the top of the tip to create a viselike effect. Roll the rest of the band down the shaft until it holds the tip firmly in place with some pressure.
9) Let the glue dry for about 30 minutes. Remove the rubber band, turn the cue upside down and trim any overlapping tip edge most carefully. Use downward strokes only with your utiliy knife so you don't mar your stick. Use a light grit sandpaper (220 or 180) to make for a very even tip. Again, go flush with the ferrule and use downward strokes only.
10) Wrap a piece of 800 grit paper around the tip area, hold in place with thumb and forefinger, and turn the cue around to get the sides of the tip in still more with the ferrule. You can finish with a 1200 grit sandpaper until the tip is incredibly smooth. Remember, start with the top of the tip then work downwards and sideways strokes away from the tip center, turning the cue beneath your sanding hand, until you have that lovely dome shaped tip you want.
11) Don't trim the tip deeper than flush with the ferrule with the knife when working the overlapping edge. (If you do it's time to start again with a new tip!) And never sand upwards against the tip with rough grit sandpaper or you face a spongy and useless tip soon.
Don't expect your tip work to be exact the first time and practice on older cues or perhaps a house cue first. If you fail, you tried, and you can always bring your cue to a pro cue repair shop instead.
Warning: Check with your cue manufacturer as certain brands like Predator shafts are meant to have certain tips applied. (In Predator's case, soft tips are not recommended for use.)