Depends on what step/stage you are in. If making a kit follow the directions. There you can't go wrong.
In the Primary I rack when the gravity is in the 1.015 range.
Secondary I wait till dry then add k-meta and sorbate and degas. If making a f-pac I may add now and later clear. If not doing a f-pac degass and add clearing agents. wait 2weeks and rack then start aging. this a rough condensed version.
We need more info to better help you like what you are making etc.
Like said above follow the kit instructions if doing a kit, if making a fruit wine then rack at around 1.015 and let finish fermenting in carboy. Once ermentation is done I rack to a clean sanitized carboy off the sediment and add sulfites, sorbate and degass. At this point you can sweeten and add fining agent if wanted or just let it clear all on its self.
Once you have racked to the secondary its really up to you. depending on the wine I would rack as needed. If that means 3 weeks then do it Keep in mind you should leave it alone for 3-4 weeks after adding clearing agents. After 3 months add 1/4tsp of k-meta.