1 UNIT unless otherwise stated. The majority of my plays are 1 Unit. If I really like a play its 2, on a very rare occasion 3. I don't like varying unit size, and I don't put 5 units a play as that obscures the true value of the record.
Everyone has their own style, but my experience is that 1-2 units per game is the best way. Its a long term grind, especially when you are playing multiple sports.
Adding......
Tennessee +7.5 (-105) (Now 2 Units, 1 at +7)
Green Bay PK (-105)