This is a guide on how to use troops as well as which troops/spells they have synergy with.

Note: This is not made by me, I found this on Supercell forums (see link at the bottom).

Barbarians
How to use them: Spread them out
Synergy with:Land troops with the exception of PEKKA, Valkyries, Hog Riders, Golem and witch
Synergy with: Jump Spells, Rage Spells
Farming Or Trophy Hunting: Farming
Type of troop: Support Troop

Archers
How to use them: Spread them out
Synergy With:Land Troops
Farming Or Trophy Hunting: Farming
Synergy With: Jump Spells
Type of Troop: Support Troop

Goblins
How to use them: Spam them, Make sure you have a meat shield
Synergy With: Meat shields (Barbarians, Giants etc.)
Farming or Trophy Hunting: Farming
Synergy With: Jump spells, Healing Spells
Type of troop: Support Troop/Clean up Troop

Giants
How to use them: Spam Them, Make sure you back them up with high damaging troops
Synergy with: Barbs, Archers, Goblins, Wizards, Healer, Valkyries
Farming or Trophy Hunting: Both
Synergy With: Healing Spell
Type of troop: Tank

Wallbreaker
How to use them: Put down 1 giant and then as many wallbreakers as required
Synergy With: All Land Troops
Farming Or Trophy hunting: Both
Synergy with: Nothing
Type of Troop: Support Troop

Balloon
How to use: Spread them out on one side
Synergy With: Minions
Farming or trophy hunting: Trophy Hunting
Synergy With: Rage Spells
Type of Troop: High Damaging

Wizard
How to use: Spread them out on one side
Synergy With: Valkyries, Witches, Golems, Giants, Healers, Barbs, Archers
Farming or trophy hunting: Trophy Hunting
Synergy With: Rage Spells, Healing Spells
Type of Troop: High Damaging

Healer
How to use: Put down your Giants/Wizards and put down your healers
Synergy With:Giants and Wizards
Farming Or Trophy Hunting: Trophy Hunting
Synergy With: Nothing
Type of troop: Support Troop

Dragon
How to use: Spread them out on one side
Synergy With: Minions
Farming Or trophy hunting: Trophy Hunting
Synergy With: Rage Spells
Type of Troop: High Damaging And Tank

P.E.K.K.A
How to use: Spam Them
Synergy With: Valkyries, Wizards, Archers
Farming Or Trophy Hunting: Trophy Hunting
Synergy With: Rage spells
Type of Troop: High Damaging And Tank/ Support

Minions
How to use them: Put them in little groups, put one down first to check for air bombs
Synergy With: Balloons and Dragons
Farming Or Trophy Hunting: Farming
Synergy With: Rage Spells
Type of Troop: High Damaging and Support

Hog Riders
How to use them:Spam them in 2 locations
Synergy With: Other hogs
Farming or Trophy hunting: Both
Synergy With: Healing Spells
Type of Troop : High Damaging

Valkyrie
How to use them: Spam them in 1 location
Synergy With: Giants, Wizards and P.E.K.K.A, Archers
Farming or Trophy Hunting: Trophy Hunting
Synergy With : Rage Spells, Jump Spells, Healing spells
Type of Troops: High Damaging and Tank/ Support

Golem
How to use them: Use them as a meat shield for other troops such as wizards or witches
Synergy with: Wizards and witches, Archers
Farming Or Trophy Hunting: Trophy Hunting
Synergy With : Jump spells
Type of Troop : Tank

Witch
How to use: Spread them out on 1 side
Synergy With: Golem, Wizards, Archers
Farming or Trophy Hunting: Trophy Hunting
Synergy With: Rage spells, Jump spells
Type of troop: Support and High Damaging

Source: Supercell Forums