Your character build can also make a difference. Duel wielding is the most effective technique for a warrior (and best for a mage - using weapons with magic damage bonuses / enchantments gives a boost to magic spells; mages don't need to invest in the duel wielding skill, since the off-hand penalty is not taken into account for the spell bonus, just melee attacks). Archery is also quite effective, especially after you get up a few levels (and useful for a warrior early to mid game, to draw opponents in and get some damage in first, rather than running or Rush Attacking into a group). Any build can use Hide in Shadows to get the first hit in, or get a break from battle to heal or regroup.
Using the Developer Mode, you can also bump your level, skills or stats up to get started, enable god mode, give yourself equipment, etc.
However, several people playing on nightmare difficulty used additional handicaps to keep the game challenging, so you shouldn't have too many problems on casual, even without using cheats. With my archer I didn't distribute any stat points after level 15, and ended the game on level 47 with 145 unused stat points, and 87 unused skill points. Another person playing a summoner type build (and using Charm) on nightmare difficulty stopped distributing stats on level 12 IIRC, didn't wear a helmet or breastplate.
