I am often asked this question, so here's a few tips that should help keep your Fantasy Football Trophy looking it's best for many years.

The best plan is preventative maintenance. Each time you dust, and yes guys, that should be at least once a month, you should give the trophy a once over. Pledge works fine for resin toppers, and bases. In terms of the engraving, that depends on the metal stock used on the trophy.
If the plates are gold with silver writing, or any kind of silver writing that is not showing signs of tarnish, you are probably looking at aluminum, which can just be buffed up with a soft cloth, so you won't have much to worry about.
Similarly, some engravers use plastic (yuk) for their engraving, again, nothing to worry about there.
For black brass, or brass in general, you are going to have more of an issue. Most engraving brass is lacquered, to inhibit tarnish, but as soon as it is engraved, the lacquer is removed, leaving your text exposed to the elements. On black brass, the black is a coating on the plate, so great care must be used not to scratch it or scuff it up. I find the best method is to use a soft cloth and Windex to clean the text, make sure it is absolutely dry, and then polish the whole trophy (including engraving) with Pledge. I think the wax helps to protect the engraving longer, the trick is to stay ahead of tarnish, especially if you live in a humid zone.
Many commercial cleaners work by removing a layer of the silver. If your trophy is silver plated, and a commercial cleaner is strong, you might strip the plating right off. I would avoid any TarnX type product. You would do best to work with a paste with no abrasives and a soft cloth to slowly work the tarnish out. Lots of patience and rubbing. Wax on...wax off....

Brass components like the trophy shown at the top of this post should be cleaned in a similar manner with only a high quality brass paste, gentle enough for brass plating, with a special cleaning cloth.
With a little TLC you can keep your trophy looking as good as new, something you and your league can be proud of for many years!
Please feel free to ask any questions, and check out my line of fantasy football perpetual trophies, loser trophies and more at Sculpture Alley!