The following rules are in play:
In all three cases, all books, supplements, and settings published by Wizards of the Coast (for D&D), and Paizo (for Pathfinder) are allowed.
In general, use the ruleset the character was built with. When rules conflict, the 3.5 ruleset prevails. Note that races, feats, and spells are not generally ever considered in conflict.
Characters are built on a 38-point buy using the 3.5 scale.
Classes from all WotC-published 3.0 and 3.5 core rules, supplements, and settings are allowed. Specifically, this includes all Forgotten Realms and Ebberon supplements. So are all classes for Pathfinder in the core rules and supplements.
Races from all WotC-published 3.0 and 3.5 core rules, supplements, and settings are allowed. So are all races for Pathfinder in the core rules and supplements.
Original starting level was 2, allowing +1 LA races. Current character level is 6.
Characters may use either action points (including the special actions available in the Eberron campaign setting), or hero points (from the Pathfinder setting), as they prefer, but they must choose only one or the other, and cannot combine the two.