Changing spell casting class into a generic class can be tricky...I usually give 'em better skill selection and/or more skill points (usually increase 'em by 2) for dropping their spells and also something extra to balance things a little.
My recommendation is to give 'em bonus feats a la fighter style from a select list that reflect the modified class (do not give them bonus feats from the fighter list unless you want a more comabative class and even them give 'em the feats sparringly minus the weapon specialization.). I did so with my customized ranger and it works fine IMC. The number of bonus feats should not be higher than the number of fighter bonus feats, or else you take some power away from the "feat master" (this is regardless of the list of bonus feats). I think around 6 to 7 bonus feats spread around evenly works best (look at samurais and monte's ranger for example...though monte's ranger is overpowering IMHO
).
Some follow the route of giving them unique abilites that define the class better (making the class more exotic and sexy). My recommendation in this case is to limit the number of such abilities to a couple and make them into abilities that adds to the flavour of the class not power (example of this is trailblazing ability of the scout? in Star Wars). Also spread out evenly.
And finally, the general
add some = take some away rule should be at the forefront of the designer's mind as he modifies/designs classes for his campaign. The power given should equal the power taken, of course.
In concusion, in the case of minor spell caster (with short list of spells and power such as paladins, rangers, or assassins) I usually change the skills, give 'em feats, and 1 or 2 abilities that adds to flavor.
These suggestion may be old news to you and YMMV
