depends on the plant. Something like a rose, you cut back to the next bud on the stem. slanting the cut so the bud is on the high side. Things like pansies, you can just clip over with scissors, or nip the heads off with your fingernails. Lavenders get the clip all over treatment but don't cut into the brown wood as they don't like it. Some marguerites are just straggly, some will stand to be clipped. if yoyu keep clipping, you will keep removing potential flowerbuds so I would tidy them up once the flowers are mostly over then leave alone again. Welcome to the club!!