3.0 DMG had Apprentice-level rules, to simulate being able to start out multiclassed at level 1/1 like in AD&D. Basically at 1st level you pick two classes and sort of get half-benefits from each (BAB, one good save, half spells, stuff like that). A primary class determines starting hit points & skills; at 2nd level you complete the level of each class and look like any other level 1/1 character in 3rd Edition.
There's a table of exact benefits from each Apprentice (1/2) level for each class, you'd need to see that in a 3.0 DMG.