This is gonna be a quick tip. I wanted to post it because I frequently use the merge command in Maya while modelling. To merge verts in Blender, the shortcut is alt + m. Conversely you can also find the merge command in the “Remove:” section of the tools panel on the left side of the ui.
To define the vertex you want another vertex to snap to you can pick one of 5 different options(at first, at last, at centre, at cursor, and collapse). I’m not gonna explain them here, as they’re pretty self explanatory - just experiment with them to see what they do :)