Follow Instructions
There are many different types of Erector sets. The 40 model Erector sets have 40 different thing you can build with detailed, colored instructions. This Erector set also comes with a 6-volt motor to literally make these models come to life. The 50 model Erector sets are similar except they have instructions for 10 more models. Observe the instructions closely and look ahead to see if there are any other materials or tools you may need to build the model more efficiently.
Lay out Materials
Once you establish exactly what pieces from the Erector set you are going to need to build each model, lay them all out to make sure you have the correct materials and the right number of pieces. There is nothing worse than getting the model half built and realize you are missing a piece. If you do happen to be missing a piece, try your hardware store or see if you have a spare in the garage or wherever tools are kept. Sometimes makeshift pieces that will hold these models together can be made, but this is a last resort. Perhaps building another model from the set which doesn't require that piece is a good idea.
WD-40 and Tightening Down
Having WD-40 or some other joint lubricant on hand to make sure the model is able to move smoothly is important, as is tightening everything down. With the lubricant, you can tighten all the different screws and nuts needed to hold the model together as tightly as possible and use the lubricant to make sure that everything moves smoothly once it is completely assembled. The tighter everything is screwed together the stronger and more durable the model will become.