Respectable = deserving respect.

• He is a man of respectable appearance.
• She comes from a highly respectable middle-class family.
• She established herself as a respectable political leader.

Respectful = showing respect.

• They stood at a respectful distance from the Governor.
• A uniformed attendant gave us a respectful salute.
• Above all, try to be respectful and considerate to old people.

Respective = relevant; corresponding; appropriate.

• All are requested to go back to your own respective seats!
• After the programme, the students went off to their respective rooms. (i.e., went to their own rooms.)
• The representatives explained the situations of their respective countries.

Respectively = in the order mentioned.

• In February and March, the profits of the company grew 20% and 25% respectively.
• First, second and third place in the competition went to Rahul, Renz and Rozanne respectively.