The back side of your table should be dead square with the column face......makes it real easy to use as a reference to face off stuff.
If you don't know the history slap a bunch of Vactra #2 on the ways before you move too much around.
Keep the oil system filled if it uses wicks.
Check the oil system out, make sure oil is getting to everything.
When cutting, lock down all the axis not being moved.
When you start cutting ,most folks start out pretty slow...lol...but these things like to feed.
Once you run it a bit, you should be able to hear how she's cutting.
Info on the web about RPM's and feed rates depending the dia of the cutter.
Arbors, hard to keep one dead perfect straight, a few thou off is no big deal as there is a bit of clearance on the cutter anyway.
Also, anytime the arbor comes apart it MUST be absolutely clean and the spacers MUST have Zero chips etc on the ends.
You are squeezing the whole mess together and anything between the spacers will/can "bend" the arbor.
Only remove or tighten the arbor nut while the arbor is in the head and the support is holding it, if you remove the support and crank on the nut....... bye bye arbor.
The arbor nut has to be pretty tight. Support should have it's own oil "tank" , just keep it centered on the support bearing.
Last for now, the closer you keep the cutter to the column and the support to the cutter the more rigidity you will have especially when making big deep cuts. There is no rule you must always have the support bearing all the way out at the end of the arbor.
Forgot one important thing: do not climb mill ........things can get very crazy really quick.