You can always start out your SMT designs with DIY laser-cut stencils but eventually you'll want to upgrade to a stenciling machine. Stencil machines hold the metal-cut stencil flat and taut so that you dont have any shifting or curling while you try to lay paste down. The good ones have a fixture so you can always get the same alignement every time - speeding up your stenciling time down to under a minute per PCB. They're a little expensive, but if you ever plan to do over 100 of a PCB they are essential!
The nice thing about this machine is that it takes framed stencils, is about $1500 after shipping and has a good fixturing area. We liked that it uses 3mm holes for alignment. Many low cost stencilers require the PCB to be flat against the bed which means you can't (easily) do double-sided boards.
We get our PCB house to place 4 x 3mm holes in each corner of our PCB panel. The first time you set it up for a PCB run, you'll need to align it by loosening the 3mm studs and placing the PCB on the fixture bed. Then you can use the knobs on the side to help align it.
It takes 5-10 minutes to set up per board but once it is set up and aligned, you can just lift the stencil, place a new one so that the corner holes snap into the fixture studs and print! We've found that the corner holes almost always line up perfectly.