Picking Up The Pots
A very easy and effective way to determine if plants need watering, is by lifting the pots prior to watering and feeling the weight of the pot. Once you water the plants you feel the difference in weight due to the water in the medium. When you have done this once, you are able to work by feeling the pot. If the pot feels quite heavy then there is still no need to feed, however if the pot is relatively light you will know watering is due soon. Once the pot is as light as the first time you lifted it, be ready to water and repeat this process every time you want to water your plants. The only time your plants will need a large amount of water is during the flushing process, towards the last weeks of the blooming stage.
Feeling For Moisture
Another useful and very easy technique is to simply place a finger down the side of the pot to feel how moist the soil is. If there is soil on your finger once you have pulled it out you will know that there is still plenty of moisture left for the plants root to grow and search for food. Be careful not to damage the roots and be sure to check multiple spots per pot so you can get an accurate reading of how wet or dry the medium is.