As a note, I have not played 4th or 5th edition, but I started with Advanced Dungeons and Dragons (about 1 year), played AD&D 2nd Edition (about 9 years), 3E to 3.5E (around 10 years), and many other games/systems (including some proprietary ones that never made it to publication and some of my own personal design). Throughout all of this time, I tended to lean towards casters and rogues, but I would play any class as long as I had a fun roleplaying idea for it.
Something I didn't see mentioned in here after skimming a bit and reading the ones I found interesting (so I may be completely incorrect about this being unmentioned, and if so feel free to ignore this) is spell weaving or spell combos. Now I don't mean that you can pick two spells and mix their attributes (though if your DM is game and your Spellcrafting is high enough, then right on). What I am talking about is knowing how spells interact with each other either after having been cast (like Grease and Burning Hands causing all surfaces affected with Grease to become ignited, though this was removed in 3rd edition I am just using it as a reference) or during casting when paired with another caster/spell (such as wall of force or bigby's grasping hand being cast to enclose a tightly grouped enemy, and then wall of fire to engulf the area with crazy damage). The spells and how they will be allowed to interact will be solely at the discretion of your DM, so I'd discuss it with him prior to the event (or at least let him know you are planning on trying some spell combinations in game, and if he doesn't think they should fly, to just have your character fail (potentially in devastating fashion if he is the malicious sort) at the cast. Outside of this, the limit is purely your imagination and your ability to interpret the unspoken rules of the spells in your DM's world.
Most players I encounter believe that wizards are weak, and in a typical engagement they usually are of pretty limited use, however no other class has the potential to destroy an army with a single spell (ex, mass illusion to create an illusion of an army attacking said army across a field, when it is actually over a large gorge), completely derail a campaign by forcing an enemy to begin explaining every detail of his plot to destroy the kingdom (though in fairness a skilled Face combined with a bit of magic through items or potions can accomplish this as well), or even creating a situation where he becomes immortal or even a God (which is actually the same exact effect to the player as though the character had died, since you now have to hand your sheet over to the DM).
Seriously though, read the spells and how the spells work in 5th edition very carefully. Think about any synergies you can see, consider adding trap synergies to the list if you have a good rogue in the party as a spell laced trap can end an encounter before it even really begins. Learn any specific caster rules the DM wants for his world. Then finally, come up with a spell list that allows for the most versatile gameplay in the system (though please stay within your character's personality scope you designed when rolling him).
Something I didn't see mentioned in here after skimming a bit and reading the ones I found interesting (so I may be completely incorrect about this being unmentioned, and if so feel free to ignore this) is spell weaving or spell combos. Now I don't mean that you can pick two spells and mix their attributes (though if your DM is game and your Spellcrafting is high enough, then right on). What I am talking about is knowing how spells interact with each other either after having been cast (like Grease and Burning Hands causing all surfaces affected with Grease to become ignited, though this was removed in 3rd edition I am just using it as a reference) or during casting when paired with another caster/spell (such as wall of force or bigby's grasping hand being cast to enclose a tightly grouped enemy, and then wall of fire to engulf the area with crazy damage). The spells and how they will be allowed to interact will be solely at the discretion of your DM, so I'd discuss it with him prior to the event (or at least let him know you are planning on trying some spell combinations in game, and if he doesn't think they should fly, to just have your character fail (potentially in devastating fashion if he is the malicious sort) at the cast. Outside of this, the limit is purely your imagination and your ability to interpret the unspoken rules of the spells in your DM's world.
Most players I encounter believe that wizards are weak, and in a typical engagement they usually are of pretty limited use, however no other class has the potential to destroy an army with a single spell (ex, mass illusion to create an illusion of an army attacking said army across a field, when it is actually over a large gorge), completely derail a campaign by forcing an enemy to begin explaining every detail of his plot to destroy the kingdom (though in fairness a skilled Face combined with a bit of magic through items or potions can accomplish this as well), or even creating a situation where he becomes immortal or even a God (which is actually the same exact effect to the player as though the character had died, since you now have to hand your sheet over to the DM).
Seriously though, read the spells and how the spells work in 5th edition very carefully. Think about any synergies you can see, consider adding trap synergies to the list if you have a good rogue in the party as a spell laced trap can end an encounter before it even really begins. Learn any specific caster rules the DM wants for his world. Then finally, come up with a spell list that allows for the most versatile gameplay in the system (though please stay within your character's personality scope you designed when rolling him).