If a monster is attacking a weak party member like a caster, stun the monster with Hammer of Justice.
Getting away (extreme)
First start running. Right before you die, cast Lay on Hands on yourself. Now continue to run. Then use Divine Shield. With these abilities you can run away for quite a distance even with a lot of monsters attacking you.
Equipment
Focus on items that give stamina and defense. You can go for a sword or blunt weapon and a shield, or a two-handed sword or mace. You might want to train up all of these abilities so you can pick and choose which to use based on what weapons you have available.
Two-Handed Weapons vs. Shield and One-Handed Weapons
Both are great. A two-handed weapon is good against monsters with a lot of armor. A one-handed weapon is better against monsters you wish to interrupt and against monsters with less armor. You might want to train both up and switch between them.
Summon War Horse
Paladins can get their own custom armored Warhorse via a quest at level 40 and level 60. Paladin Epic Mount quest: To begin, talk to the paladin trainers Duthroian Rall or Brandur Ironhammer. Paladins who have completed their Epic Mount quest can repeat the final event in Scholomance for fun (and loot) by speaking with Lord Grayson Shadowbreaker.
Profession Options
You can pick whatever you want. You might find these more tailored to the Paladin: Mining and Blacksmithing - Paladins can create their own armor. This is a popular choice with Paladins.
Mining and Engineering - Paladins can create range weapons and special engineering items.
Enchanting - Paladins can enchant their equipment to make themselves more powerful.
Herbalism and Alchemy - Paladins can create buff potions or healing potions.