I am going to ASSume the following

1. You are prepping both the cap and pipe you're trying to cap (they sell brushes specifically for this)
2. You are using the correct flux on both the cap and pipe
3. You are using a full bottle size torch, (Mapp gas burns hotter)
4. Have the torch lit
5. Stuff a decent amount of bread in, (no crust) quickly push it in the pipe with a dowel rod. push a second wad in if desired
6. Cap the pipe
7. Heat upper portion of the CAP all the way around if possible. If wood or other combustible material are near by, use a good sized metal sheet to shield it and disperse the heat
8. Put the solder to the lower edge of the cap and it will draw the solder up towards the heat.
Sounds way more complicated than it is

Also if your valve is leaking before the meter, the water company should repair that at their cost. That will then allow you to repair/ replace the inside valve. I have also had luck in the past by closing and opening the valve a turn or so several times