Perhaps the most important thing is to make sure the wood is uniformly sanded prior to staining. Any uneven sanding will give uneven stain results. Also don't over sand before staining. You want a little tooth for good stain penetration. I don't use a sealer. Instead I use varnish thinned 50%, then 25% then at least 6 coats of minimally thinned varnish. That gives a total of 8 coats of varnish minimum for mahogany. I think 10 is better followed by 2 coats every year.