1. The causative has the meaning of 'someone causes someone to do something'.
2. The three verbs usually used for the causative are get, have, and make.
a. John got Susan
to rake the leaves.
b. John had Susan rake the leaves.
c.John made Susan rake the leaves.
Notice in a that there is a to in to rake.
Notice in b and c that there is no to.
3. Get gives the idea of persuasion, have is asking, and make is forcing or strong convincing. There is not much difference between have and get.
4. These causative verbs can be in any verb tense:
a. I am making my students write the exam again next week because they did so poorly.
b. I have been having my kids shovel the sidewalks after every snowfall.
c. I have to get my wife to pick me up after work because my car is in for repairs.