From my NASA High Reliability Soldering Certification course: NASA certification was developed after a failed launch of a space craft. The cause was determined to be excessive solder
throughout the craft. 300 pounds more solder than needed!!!
These are some random tips that come to mind;
The very first rule is to use as little solder and heat as possible to obtain a reliable joint. If you examine the joint closely you should be able to see the shape of the parts of the connection with a smooth transition. In other words the solder should conform to the shape of the connection.
Soldering is easy, but it requires practice of proper technique before you attempt a serious project. Use scrap wire and components to practice.
Make sure that your connections are mechanically solid prior to soldering.
Use a vice, forceps, clips, or some other method to hold the work firmly so you don't have to chase it with the soldering iron.
Use alcohol to clean up if you use rosin core solder.
Do not ever use any type of acid core solder or flux on electronics.
If you are concerned about lead in your e-cig then use lead free 'silver solder'.
When working in tight spaces avoid tunnel vision, watch out for the soldering iron getting too close to other components.
Avoid overheating by pre-cleaning, tinning, and use flux. This will help make the solder joint quickly to allow minimal heating.
Drip works for
vaping, but NOT for soldering.
Heat the connection and let it melt and attract the solder rather than trying to use solder as glue. Use a tiny bit of solder on a clean tip to help conduct heat to the connection faster.