How to weight my model so it does not tip?

For wargaming figures, a small coin or washer glued to the under side of the base will usually to do the job. This may also work for larger static based models.

However if you are going to be weighting your rolling stock or a plane, a more precise approach may be called for. Deluxe Materials have the answer: it is called Liquid Gravity.

It is made up of very small metal balls not unlike lead shot but without the lead and can be positioned in exactly the right place. Add some cyano glue (super glue) and the balls are held in place.

Very simple and very effective and should do away with those annoying derailments as well as help pull more coaches and wagons.

Liquid gravity can also be used for weighting radio-controlled planes and cars or even wargaming figures if you need the extra precision.