When using advanced combat strategies in Dungeons and Dragons (D&D), it is essential to understand the unique abilities and spellcasting options available to each class to make the most out of them. Here are some advanced tips for barbarians, monks, fighters, rogues, and rangers, to help you optimize your character's combat abilities:

Barbarians: Barbarians are known for their raw strength and rage abilities, which allow them to deal extra damage in combat. To make the most of this, consider taking feats that enhance your rage abilities like "Brutal Critical" and "Persistent Rage" this will allow you to roll more dice and apply your rage damage more often. Also, consider multiclassing into a class that provides more durability, like a Paladin, to complement your rage and increase your survivability.

Monks: Monks are a unique class that combines martial arts and spiritual discipline. To make the most of this, consider taking feats that enhance your unarmed strikes, like "Kensei" and "Deflect Missiles" this will allow you to deal more damage and improve your chances to deflect ranged attacks. Also, consider taking spells like "Mirror Image" or "Blur" to increase your evasion capabilities, and take advantage of your high movement speed to reposition and strike from unexpected angles.

Fighters: Fighters are a versatile class that excels in combat. To make the most of this, consider taking feats that enhance your weapon proficiency, like "Great Weapon Master" and "Defense" this will allow you to deal more damage and improve your defences. If you have access to spells as an Eldritch Knight, spells like "Shield" and "Haste" can be a great addition to your kit, providing more survivability and action economy.

Rogues: Rogues are sneaky characters that excel in stealth and deception. To make the most of this, consider taking feats that enhance your sneak attack, like "Sneak Attack" and "Assassin" this will allow you to deal more damage when attacking from surprise or flanking. Also, consider taking skills like "Thieves' Tools Proficiency" and "Deception" to gain more versatility and interact with locks, traps, and NPCs more efficiently.

Rangers: Rangers are proficient at both ranged and melee combat. To make the most of this, consider taking feats that enhance your combat style, like "Hunter" and "Archery" this will allow you to deal more damage and improve your accuracy with your chosen weapon. Also, consider taking spells like "Barkskin" and "Hunter's Mark" to buff yourself and your allies while dealing extra damage to your targets. Also, consider taking the Natural Explorer feat to boost your tracking and survival skills, making you an invaluable party member in the wilderness.

These are just some advanced tips to help you optimize your character's combat abilities. Remember that D&D is a game that encourages creativity, and the best way to determine what combat strategies work best for your character is to experiment and see what works best in the context of your campaign.

Additionally, it's crucial to coordinate with your party members and come up with a cohesive strategy that leverages the strengths of all the characters. This way, you can create powerful combinations and execute them effectively.