Stain / Protecting wooden boards

[WB72]

I have my wooden bed boards stained, and plan to clear coat them. Do you think 3 coats of exterior grade Marine Varnish will be enough protection?

The can says: Thin first coat 10%, apply a generous coat, a second coat should be applied 8 - 12 hours later. A third coat can be applied if desired.

I think three coats will be sufficient.

I have the boards all cut, grooved, and drilled before I stained them.

Is there anything that I should be aware of before I start this process? I would hate to screw up the oak boards before they are in place.