Here is how I do mine:

I built a small jig by screwing two wooden cloth pins (the ones with the metal spring to open and close them).
One of the pins is used to hold the dean connector and the other one holds the wire in place.

Slip shrinking tube over the wires.
Connect the one you are preparing to another dean connector. So, if you are going to solder a male connector, plug it into a female connector. If you overheat the connector, it will not melt and it will retain its shape.
I then tin both posts on the dean connector. Don't tin the wire.
Strip the wire and, using an exacto knife, split the wire into two halfs flattening both halves (using long-nosed pliers) with the blade in place.
Slip the dean connector tab in the middle of the two halves, so that the wire fits snugly on both sides of the tab.
Melt solder on the connection until it is fully covered and looks shinny.
Slip the shrinking tube over the connection and heat it as usual.

This is perhaps a lot more than you asked for, but it really works well for me.