Understand that Maximizing one aspect of your character frequently comes at the cost of crippling another part of your character. Be aware of character weaknesses then build in additional strengths to help cover these weaknesses.
For instance, the recommended building option is to start with an 18 or 20 in your primary ability score. It costs a lot of points to do that. You character is going to have lower saves or hit points as a result .
Understand this result and build in extra features to minimize the effect of this lower survivability. Consider playing:
1. a class or multi-class that has inherently good saving throws. i.e. monk, paladin (and others)
2. a race that has bonuses to saving throws or constitution
3. a race and class that can spend action points in enhancements that increase your character's survivability.
4. a class that can self-heal. Healing others is great. Self-healing is super.
5. a class that has evasion. Taking reduced area effect damage in DDO is huge.
6. a character that can solo well-enough (with the help of a hireling) so you can earn gold by farming quests and explorer areas. You want to be able to buy lots of potions and scrolls and other resources to protect your character. Have a rich friend!
7. a character that can slay monsters while being beyond the reach of monster melee attacks.
You do not need to have a character that does ALL of the above in order to succeed in DDO.
Teamwork, game knowledge, and smart play is more important to success than character building. Practiced arcade-reflexes help a lot too.