I feed every watering usually, once a month or so doing a flush with plain water.

If you start seeing problems, try to clear out the nutes like others said and either go to every other watering or half strength at each watering until you come upon what works for your situation.

Every grow is different and you have to take into account things like the pot size, soil type, nutrient formula/strength, lighting, and strain grown when adjusting your feeding schedule. Some plants can eat up as much as you can give them and others can't really handle anything, soils have some nutrients in them already and sometimes can have enough where you don't need to give any additional nutes for 3 months or more, larger pots will hold onto nutrients a lot more and can build up with salts easily if overfed, lighting and co2 are two of the 3 things (along with nutrients) that the plant uses the most for growth and if either is lacking too much then adding more nutrients won't do any more good.

With a little trial and error you should get it down pretty well, it's not too hard: it's just finding the proper balance.