I usually water my plant wait 2-3 days then stick my finger roughly 3 inches into the soil, if it feels moist i let them be. next day feel, check again if dry to the touch(little if any moistness) water. Then pick up your pot when freshly watered to get a feel for its weight when watered. Once you get a feel for a freshly watered pot you will just know by picking it up in the future in collaboration with your good old finger
You could get a moisture meter but i think its unecessary in my opinion. I usually let about an ounce and half of water run out from the bottom of the pot per 10 ounces in...roughly i use 2 gal pots so i water using about 20% WATER FOR THE AMOUNT IN SOIL so it works out to be about 50 oz of water for a 2 gal pot.