There are a number of concerns when coordinating the actions of multiple characters.
Combined Tactics
When coordinating the efforts of characters with many and varied skills (as commonly happens in adventuring parties) there are many options available
Spellcasters
A lot of options are created or denied when a spellcaster chooses his spells. For a Wizard or Cleric this choice is made on a daily basis. For a Bard or Sorcerer this is done at will, but with a limited number of spells to choose from.
If the opportunity exists, discuss daily spell selections (or new spell learning for Sorcerers) with the party ahead of time. If your Fighter is counting on a certain kind of backup from the spell-hurlers, please endeavor to provide it, or make sure he doesn’t expect it.
Ranged Combat
Extra work needs to be put in to use Ranged Combat effectively in combat. D&D is set up to encourage a degree of toe-to-toe melee action in combat. Many of the monsters use melee effectively and can be foiled by ranged weapons if circumstances add up properly
Keep them away
If at all possible, use terrain, magic, and tanglefoot bags to keep your enemies away from you. Once they close in within reach of their melee weapons, ranged combat and spellcasting become far less appealing.
Useful spells for this purpose include Entangle and Hold Person.
Terrain features such as ravines, cliffs, walls, and rivers can buy you time as well against most opponents.
Tanglefoot bags were literally made for this purpose. Your campaign world may include other alchemical means of slowing down an enemy’s advance into melee as well.
They’ll Get to You Eventually
Don’t count on always being able to drop your opponents at range before they get to you. Have defensive magics and melee weapons handy for the inevitable. If your party did a good job slowing the enemy advance, you’ll be dealing with a softened-up opponent
Defeating Ranged and Reach Opponents
When magic isn’t an option, charging is the way to go to close a gap quickly. If your opponent has advantage over you be means of terrain, don’t underestimate the value of retreat. There’s no dishonor in it, as ranged combat isn’t a Manly way to fight anyway, and you may be able to lure them to a location better suited to your capabilities
Magic to defeat Ranged opponents is many and varied. Obscuring Mist is the bane of many an archer who has had to cope with the concealment offered by such a spell. Concealment also foils targeted spells, and can be provided by invisibility magic as well. Dimension Door, Teleport, and other movement spells can instantly close the gap between opponents, and Fly can get around most terrain advantages rather easily.
Flanking
Suck it up, take the attack of opportunity and flank that sucker. Send your toughest damage-soaker (preferably high-AC, high-HP) to the opposite end of an opponent. By focusing a high-AC fighter and a Rogue’s Sneak Attack against a single opponent, you are likely to make short work of the matter.
Remember that you need to be exactly across from your opponent to gain a flanking bonus
Overrun & Spellcasters
You know exactly why that Wizard brought a fighter along with him: to keep you away form him. Don’t let that disuade you
Send one or more melee types (preferrably with Mobility) past the enemy’s melee types and straight to their fragile spellcasters. You are likely to soak an attack of opportunity, so pick you path wisely. Don’t take any more attacks than you really must. On the tail end of your move action, ready an action to attack the spellcaster if he attempts to cast or move, and you may even interrupt a spell while you’re at it.
With any luck, your opponent’s melee types will fall back to defend their spellcasters instead of pressing on to yours. This works well when the spellcasters are the most capable opponents on the field: your spellcasters may be able to deal with the hired help just fine.