Use the strategy guide if you want general, vague tips on what to do. Other than that, actual written FAQ/Guides are your best bet. You need to concentrate on a chosen skill, or two, for a given character
from the beginning! As with any RPG... Level! Level! Level! If the regular enemies are tough, the area boss may be too much. If the regular enemies are cake, the area boss may still pose a challenge.
Beat the game twice! The better ending is unlocked via story elements presented in a dungeon unlocked by beating it the first time. Any and all metal slimes are open game for quick experiance, if challenging. You will need them to level up and unlock the second ending. The final, secret dungeon is tough!
The alchemy pot is your friend! If you don't know what it is, learn quickly. The best items can only be created!
Each character has his or her place. Learn it or create it. They can change roles based on skills, so choose carefully. Get a skill to 100 points, maximum level, as soon as possible. It's often best to split between two skills (a weapon and the personality skill is my personal choice) due to character level to skill point limitations.
If at all possible, be conservative about magic use until you get to the area boss, then let loose! If you're forced to use all your MP before you get to the area boss, you won't be able to pull off your best skills or magic.
Getting back to the area boss, know its type! If you have a skill to trump the boss' type, use it! You will lose the battle where you don't know to trump. In fact, know regular enemy and special enemy types. Knowledge will serve you well.
Dragon Quest is more about skill and knowledge than level. The strongest team will lose to the strongest enemy unless one knows how to tense-up quickly and painlessly. Do not give certain bosses a chance to reduce or eliminate your tension! There is an item to help later in the game, but you must still know the formulae
Judge the next area by the boss you just beat. You're about to meet tough oposition!
Know your modes of travel and areas accessible. Again, knowledge is key!
Remember, knowledge and skill can often overcome a lacking level. You need levels to earn skill points to spend, so spend them wisely! You only get a limited, precious few! You should still have one or two skills at or ready to breech 100 points, maximum level, by a character level of between fourty-five and fifty. This may include a diversion or two to pick up exceptional skills, like Helm Splitter.
I think that's it from me...for now
I can give more specific details, but that may involve spoilers...and skill breaks. I.E. Hurt the gaming experiance for you.