A several additions to Olyj1947's excellent suggestions:
1 - With the plugs out, squirt a tablespoon or so of engine oil into each cylinder.
2 - While the rocker box is still off liberally oil the rockers/valve stems. (I simply pour a quart of so of oil over everything under the box....)
3 - Before hitting the starter, bar the engine over a couple revolutions to spread the oil and insure there is no internal problem preventing rotation. If you have the hand crank, use it for this(!)
4 - With the plugs still out, roll the engine with the starter until the oil pressure gage starts to move. This insures oil to the main and rod bearings before the engine fires.
Good luck - the W4 is a good tractor!