Here is another quick tip for you. It’s a feature that you don’t easily find when you’re just fiddling with SolidWorks, it basically has to be pointed out to you by someone else (thanks Ryelle!).
My previous procedure for mating the first part of an assembly
I am very detail oriented when I am setting up 3D models. That is why the part/assembly at the top of my assembly tree is always the main component. It can for example be the frame of my machine, or the surroundings where the machine will be installed.
When this component is inserted, I immediately remove the fixed position property (right click > Float) because it looks like a lazy person just left it there. Then I add three mates: Front Plane to Front Plane, Top Plane to Top Plane and Right Plane to Right Plane. It is a chore to do this every time, but there is no other option. Or is there?
Introducing: the Coincident Origin mate
There is a hidden option when you create a Coincident mate and it only reveals itself when you select two origins. It doesn’t even work with regular points. You can see two versions of the mate window below. The version on the left is the one you have seen a gazillion times, the one on the right shows the hidden option.
You will have to make another choice now. You can make the two points coincident just like you can do with any other two points, or you can align all three axes and make all three planes of two components coincident to each other. The last one will save you from adding two extra mates for all planes, and who can say no to that?
Mating two origins is ideal if you design parts with a common origin for example, or for quickly mating the first part in your assembly.