Regardless of the method of preservation used the first thing which must be done is to clean and restore the teak to its natural state.

At BoatDocs1 we believe in accomplishing this in the gentlest way possible while still achieving the desired results. If the teak is just dirty a thorough cleaning with laundry detergent, chlorine bleach, scrub brush, and a little elbow grease will do the job.
 
If the wood has weathered for long, has remnants of a previous sealer, varnish, lacquer, or the like, and/or if mildew has set in we will have to use oxalic acid to kill the organisms, bleach out the black and stained areas, and deep clean the wood.

If you are doing this yourself the main thing to remember is that anything remaining from a previous product will interfere with the bonding of the new coating.This can cause anything from a minor color shift to causing the new coat to not stick at all and actually blister and peal away from the surface.

So take your time, use plenty of water to rinse away all of the soap and residue of previous products and allow at least 24 hours drying time before your first coat.

As with any paint, lacquer, or varnish, it is the preparation that sets the professional results apart from the want-to-be attempts.If you figure on about a 80%/20% ratio for preparation to application you should be pretty close.
 
Everybody and their dog can swing a paint brush but it takes a little savvy and a good bit of patience to hold off on the brush till the wood is ready.Without that forbearance the job is doomed before the can is ever opened.

Now the choices begin.