For me with fruit wines the key is that the wine is clear I check the bottom after each racking to see if and sediment is still dropping. Once there is no sediment then I start thinking about bottling. You also want to make sure that no co2 is left. Tasting it to see if it is flat or has zip will help determine that.
As others have said when back sweetening please do taste tests. Make up a simple syrup and the start doing ratios so you know at what point you have added enough syrup to bring out the flavors you want. One think to remember is go a little lighter on sweetening than you think because the wine will age in the bottle and get slightly sweeter.