Assuming you pick a good day for doing the job, for me the keys to a good caulking job are:
a. completely clean out the caulk you want to replace.
b. remove all remnants of old caulk and wipe joint clean using a little lacquer thinner on a rag.
c. mask the edges of the joint with masking tape. For typical large joints, I like to put the edge of the masking tape about 1/4" to 5/16" from the joint corner.
d. find a good place to start and stop the joint.
e. apply the caulk to the seam using a caulking gun, slightly overfilling the joint. If the caulk is drying too quickly to tool easily, you may want to spray a light coat of mineral spirits on the caulk right behind the caulking gun.
f. use a round object such as the piece of plastic pipe shown in the pic to tool a perfect concave joint, see pic. You may have to try several different "tools" to find just the right one .
tool-c - Photo Gallery
g. try to tool the joint in one continuous stroke. It's ok to go back over a joint to smooth it out. If the tool drags in the caulk, it may help to use an old windex bottle to spray a light coating of mineral spirits on the caulk just before tooling.
h. immediately after tooling, remove the masking tape, pulling the tape out and away from the joint, trying not to let the tape touch the freshly tooled joint.
i. throw the masking tape you just removed into the trash immediately, so it doesn't contaminate the work area.
This system works good and produces professional results.