BEFORE you connect the gas hoses to the kegs, put it all together, pressurize it and then close the valve on the bottle. If 24 hours later the pressure hasn't dropped you're good to go. If it has, start looking for leaks with Star San or soapy water. (the former is better as you don't want soap near your beer).
Sanitize your keggies. I have a compressor and made a gas and liquid hose with ball connectors on one end and nothing on the other. I clean the kegs, then rinse. Put the air on the gas line and force water out the liquid side. Repeat with sanitizer.
Store the keggies with sanitizer in them, pressurized with air. Keeps the seals seated and alerts you if they lose pressure to look for leaks.
The most reliable way to carbonate is with the bottle. On service pressure for a week to ten days and you are good to go. If you're in a hurry you can hook the keg up at 30psi and gently roll it back and forth (end to end). You will hear the CO2 go into solution. 20 minutes or so. Pull the pressure relief vent on the top of the keg to relieve the high pressure and then hook up service pressure. It won't be perfect but it will be drinkable. Depending on how it is you can also leave it hooked up to high pressure for another day and then drop to service pressure, or just hook it up at service pressure and in a few days it will be just right. Play around with this, you're get the feel for it.
One caution, if you have another keg hooked up, disconnect it when the pressure is cranked up.