I have played in a few different level campaigns as a spell caster and very seldom did I overshadow the non-casters. I think the important thing was that we played day by day, not encounter by encounter. Depending on where we were we could expect up to 6 encounters during a day & night cycle. Sure we might only have one, but I couldn't simply unload, because I never knew if that was the last encounter of the day.
Casters in D&D are limited by what spells they have available to them, try to keep the encounters balanced so that a variety of spells are required, to keep the casters on thier feet. Sure they can load up on combat spells, but then they are out of luck when they need divination or travel or other non-combat spells. Also run some adventures that have a time limit : a portal that is only open during certain conjunctions, a quest that must be completed before a marriage, a mission to prevent a war - even as the armies are marching to the battlefield! A wizard is very powerful if they are allowed to bring thier whole arsenal of abilities into play, but by making the players play on your field rather than setting up the fight to thier design you can make the wizard the important but not dominant member of the party that he should be.
Another concern is spell availability, in an already running game this is a little hard to control, but if you are just starting a game you can restrict what spells are lying around and force the wizard to use their new spells per level to gain the spells they want/need. Even there you can change restrict that and make the player research all their spells, then it becomes a matter of balancing the money in the game vs the cost to research a spell.
A few ideas for balancing wizards (and to a degree other casters) without changing the whole game system.
Casters in D&D are limited by what spells they have available to them, try to keep the encounters balanced so that a variety of spells are required, to keep the casters on thier feet. Sure they can load up on combat spells, but then they are out of luck when they need divination or travel or other non-combat spells. Also run some adventures that have a time limit : a portal that is only open during certain conjunctions, a quest that must be completed before a marriage, a mission to prevent a war - even as the armies are marching to the battlefield! A wizard is very powerful if they are allowed to bring thier whole arsenal of abilities into play, but by making the players play on your field rather than setting up the fight to thier design you can make the wizard the important but not dominant member of the party that he should be.
Another concern is spell availability, in an already running game this is a little hard to control, but if you are just starting a game you can restrict what spells are lying around and force the wizard to use their new spells per level to gain the spells they want/need. Even there you can change restrict that and make the player research all their spells, then it becomes a matter of balancing the money in the game vs the cost to research a spell.
A few ideas for balancing wizards (and to a degree other casters) without changing the whole game system.