when to water?

without a moisture meter (havnt got one yet) how do i avoid over watering until i get one?

The best bet is to water them every 3-4 days. Its not going to hurt them if you let the plant wilt a little from lack of water. Besides that way you can lift the pot up to get a sense of how heavy it is when dry. That will be your best way for determining when to water. If you lift the pot and its heavy your good, if it feels light you know you need water. Maryjane does best when its given a wet to dry cycle. Its bad to never let the soil dry, when the soil is damp it locks the oxygen out.

thank you very much that was much useful, but i will still invest in a moisture meter.

how often to water depends on how much you water, how big your pots are, how much light/heat your using, and how large your plants are asuming your in the early stages I wouldn't go 4 days without watering. Just stick your finger in the soil an inch or two and if it is dry water. The water meters are very easy to use though and are pretty accurate so you will be able to get yourself on a better schedule once you get one.