Chris Brantley has collected this list of rules variants for the De Bellis Antiquitatis (DBA) ancients miniature wargame.
David Kuijt has instructions on building terrain squares for DBA miniatures games.
Chris Brantley has a page with advice on scratch-building wargames terrain. It’s aimed at newbies in general, and DBA players in particular.
The Solitary Wargamer offers a variant of DBA for the English Civil War.