Depends on the plant, because carnations will root in water, pelargoniums just need a pot of soil, and fuschias need heat, rooting powder and high humidity.

But just get some rooting powder, a pot, some seedling/cutting compost and some celophane, oh and a stick.

Put the compost in the pot, take the cutting, remove lower leaves, cut it cleanly, dip in rooting powder, put into pot of compost (make hole and insert, just pushing it in will damage the cells around the base where roots will grow) then put the stick in and pur the cellophane around it, like a wigwam, to keep the cutting moist.

U will need to wait till the end of June, for the bush to finish the first flush of blooms (although you can root it before it blooms, but then u don't get to see the bloom, so i like to have the cake and eat it and wait till it's finished blooming) Now u have what is called semi ripe cuttings, which are best. follow directions above, but be sure to read (google search) for Cheryl Netter, and George Mander. George has it down to a science (or down to an art). I basically do like what George says, which is basically what sirilucky above describes, but in no so much detail. U MUST prevent the cuttings from drying out by some kind of plastic cover (I actually buy something called a Humididome, which is made to cover a standard 11x21" tray.
There are some older threads from way back on this site, I believe there used to be someone called "object16" that used to post here, but I think he passed away, but if U do a search for his threads i think they may be of use.

Here is a link that might be useful: A nice thread by the late object16, about rooting cuttings.