Make sure you always monitor your level and make sure that most of the points are used. Keeping one or two extra points on hand in case you need to increase your strength or your observation skill is not that bad of an idea, but if you increase your observation skill by one each time your level increases until it is 5 then you will not have any problems finding the secret doors.
If you look at the charts above you will notice that the maximum strength needed to use all the items is 19. There is no need to increase strength beyond this point.
Make sure you equip more powerful items when you find them. If you do not have the strength to equip the items, then make sure to increase your strength the next time you advance in levels and then remember to equip the better item.
Save the game frequently! It is an application specifically so you can save the game!
Slowly add to Strength (2-3 points per level) as you wont find the more powerful items until later in the game.
I find it best to focus on only one combat magic skill (energy or fire) and max it out before focusing on other skills (exception being observation and strength).
Keep mage rings in your inventory and wear them only when you are about to cast a spell of that type. Remeber that switching items in the middle of combat doesn't have any penaly in this game (future Coffee Quests may be more picky about this)
Let monsters approach you (using arrows or magic on them as they advance) so you can get the first swing in.
Always make sure that you have thoughroughly explored a level before going on to the next level. The only possible exception to this is when the only unexplored areas are not reachable, in which case there are probably secret doors that lead to them but nothing behind secret doors is vital to finishing the game.
Did I mention that you shoule save the game frequently?