A light feeding with an all purpose fertilizer is beneficial to new plantings to get them established. A feeding of a low nitrogen fertilizer may be needed later in the season. Geraniums need a cool winter for best development. This is the resting period for most types. If you keep these plants blooming all winter it will weaken the plant and it may not perform next summer.
Geraniums are basically plants from a dry climate although few tolerate arid conditions.
It is important that the soil drains well and that water doesn't stand around them. Infrequent deep watering of bedded geraniums is better than frequent light sprinkles. Water potted geraniums only when the soil is dry. Anything less than full sun will result in a poor specimen. Indoors, keep them as close to a southern window as possible.