Shamelessly use the portal spell, especially in the early game, when leveling up happens more frequently, replenishing the mana pool.Place different dishes on tables, or dwarfs will get bored of the same food and not eat.Mages will use health elixirs automatically.Improve the comfort level of your shelter by replacing home walls with wood and then better materials.Dwarfs without a bed are unable to sleep. Try to fight enemies while they are spread out, by catching them with a portal spell.Archers can do damage from distance, but cannot fire unless the enemy is 2 blocks away.Use magic fireball and other offensive spells to aid the dwarfs if they are swarmed.Dwarfs will run if hit too often from both front and back, avoid this by taking control of the dwarf.
Use the swordsman/archer/mage skill books as soon as you get them, so that your dwarfs will deal more damage.Seal your base under three layers of dirt, only venturing to the surface using the portal spell.Spikes are so good at delaying hordes but consume resources, so limit your their use too (creating many 2*2 stone block pits from both base sides are more effective, and some stone can be retrieved after it is destroyed).Note that traps will be consumed in the process and re-crafting traps will quickly deplete your wood/iron resources, so limit their use. Wisely use wooden/iron traps to kill/injure monsters and to kill animals near your base, instead of running after them.Use wood/ iron cages to hold monsters and delay them as much as possible.Sand walls may be used as a good defensive setup.Most monsters cannot climb, unless they find a shield stair.
You can create pits around your shelter to trap monsters.Use stone loopholes to reduce the damage received. Ranged enemies like skeleton archers though can shoot through the door/hatch and damage dwarfs. While melee monsters are attacking a door/hatch, you can attack them from inside safely without getting damaged.Dying in lava destroys equipment (armor, weapons, etc.) rather than leaving loot that other dwarfs can collect. When a dwarf falls into lava (the bottom of the "world"), it takes severe damage and dies unless they manage to get out.Stay away from guardians until you have mythril weapons.Use beware sign to limit and prevent dwarfs from moving into dangerous locations, like deep waters, heights or enemies.And as a bonus, loot weapons can be disassembled to iron ore & other materials. Leave one or two graveyards as you may need to kill the spawned skeletons to get skeleton's bones for crafting and for keeping your dwarfs challenged, improving their fighting skills. Or do it during night to get some extra easy experience. Do it during day time so any spawned skeletons die immediately. Destroy graveyards as soon as possible in order to reduce the number of skeletons you encounter during night time.