A dab of non corrosive flux paste works wonders, just apply a thin film to the
surfaces to be joined and remember to clean the board with an appropriate
Make sure you have a decent clean soldering iron 'bit' and just as you are
about to make the joint dab a little solder on the bit, [enough to create a little bulge of solder but no more]
and then apply the bit to the parts to be soldered , trying to ensure that
the tip contacts both parts then introduce some fresh solder to the heated
If all is correct and heated properly the introduced solder will just snap into place, so to speak!
Another method is to load the iron with a just about enough solder to make
the join [if it is sufficiently small] and press the blob onto the parts to be jointed.
The above technique is fine if you are quick enough to prevent the solder
from oxidizing [when the blob discolors and skins ] but best reserved
for tiny solder joints that can be done quickly.
But ultimately one really just needs to practice lots and familiarize oneself
with how the solder behaves.
Practice, practice, practice.........Perfection