All summer flowering herbaceous plants should be regularly deadheaded (unless seed heads are a feature) as this prolongs the flowering period and prevents plant's energies from being diverted into unnecessary seed production.
Tall herbaceous plants
60 cm+ such as Delphinium, Lupin etc MUST BE STAKED. These need staking early in the summer using tripods of sticks with string or wire hoops. They then careful attention when growing to ensure they do not 'flop' over. Staking must be gradually raised, as the plants get taller.
Medium-sized herbaceous plants
up to 60cm such as, Geranium, Nepeta etc: Where growth becomes leggy, especially after flowering, trim back flowers and foliage if required to promote bushy growth.
Herbs & Crevice plants
Generally, herbs & crevice plants need to be kept neatly trimmed to avoid them getting too straggly or leggy. This is best done after flowering & again in the spring if necessary.