1) Be prepared for the long haul. This class is balanced... for level 15+. You will notice that Rallying Cry scales to level perfectly, but Inspiring Surge has a drastic increase at 17/18, and Bulwark at 17 as well. Before that, those skills are going to be limited. Fret not, there's ways to make it work for you early on.
2) Do NOT get Resilient Int/Wis/Cha Feats. You need to fail these so it triggers your Indomitable (and therefore Bulwark) when needed. The reason you need these to fail? Because you can't help your friends if you succeed. So this is a little meta-game-y, but this is how the feature is designed so use it wisely. If you fail at these Saves and your ally fails, this is a chance for you BOTH to succeed. If you succeed and they fail, you've got no way to assist. I suggest not dumping a stat, and keeping them at least at 10 or 12 at least.
3) One of the best Faces in the game. The only one with 4 attacks per round. If you're lacking a Bard or other Face in the group, this class is one of the best in the game. Expertise in Persuasion is highly-sought-after and gives you a good opportunity to come through in a pinch.
4) Inspiring Surge at the right time, and the right allies. This is where things like Shove prone and Shield Master Shove come in handy. You and a rogue hacking away at a monster's seemingly limitless health pool? Shove prone on your turn, then Action Surge so you AND the rogue can put in a devastating round of blows while its down.
5) Subclass Design similar to Champion. Notice how Champion and PDK don't give you any more Bonus Actions or Reactions? Yeah, you need to fill those with Feats or abilities, fast. Shield Master, Healer, Defensive Duelist, Sentinel, Dwarven Toughness - anything you can think of that adds to your Action Economy outside of Second Wind and Action Surge. Better yet, go for Two Weapon Fighting at the start to ensure you always have a use for your Bonus Action.
6) Rallying Cry. On the spreadsheet it's clear: This is like your own personal pool of healing equivalent to (Level * 4) + 5.5 on average. How does it compare to Lay on Hands? Well, this recharges on a SHORT rest, is worth almost as much, and can be used on all targets in a 60ft range simultaneously, as a bonus action. This blows Lay on Hands out of the water.
7) Races - Half-elf, Drow, Eladrin, Tieflings Aasimar, and Humans (Variant) seem to mix well with this one. My personal recommendations?
a) Triton - Str bonus, Con bonus, and Cha bonus FINALLY works for a class. Plus you get some resistances, Swim speed, and some other cool stuff.
b) Human (NON-variant) - Get a 12 in Int, Wis, and Cha (for a +1 in Saves for each one) then max out Str/Dex and Con. All-around this will help with Bulwark much better in later levels.
I haven't written a strategy post for the less-desirable classes in a while, so here goes...
First, the spreadsheet I'll be referencing below.
Tips:
1) Be prepared for the long haul. This class is balanced... for level 15+. You will notice that Rallying Cry scales to level perfectly, but Inspiring Surge has a drastic increase at 17/18, and Bulwark at 17 as well. Before that, those skills are going to be limited. Fret not, there's ways to make it work for you early on.
2) Do NOT get Resilient Int/Wis/Cha Feats. You need to fail these so it triggers your Indomitable (and therefore Bulwark) when needed. The reason you need these to fail? Because you can't help your friends if you succeed. So this is a little meta-game-y, but this is how the feature is designed so use it wisely. If you fail at these Saves and your ally fails, this is a chance for you BOTH to succeed. If you succeed and they fail, you've got no way to assist. I suggest not dumping a stat, and keeping them at least at 10 or 12 at least.
3) One of the best Faces in the game. The only one with 4 attacks per round. If you're lacking a Bard or other Face in the group, this class is one of the best in the game. Expertise in Persuasion is highly-sought-after and gives you a good opportunity to come through in a pinch.
4) Inspiring Surge at the right time, and the right allies. This is where things like Shove prone and Shield Master Shove come in handy. You and a rogue hacking away at a monster's seemingly limitless health pool? Shove prone on your turn, then Action Surge so you AND the rogue can put in a devastating round of blows while its down.
5) Subclass Design similar to Champion. Notice how Champion and PDK don't give you any more Bonus Actions or Reactions? Yeah, you need to fill those with Feats or abilities, fast. Shield Master, Healer, Defensive Duelist, Sentinel, Dwarven Toughness - anything you can think of that adds to your Action Economy outside of Second Wind and Action Surge. Better yet, go for Two Weapon Fighting at the start to ensure you always have a use for your Bonus Action.
6) Rallying Cry. On the spreadsheet it's clear: This is like your own personal pool of healing equivalent to (Level * 4) + 5.5 on average. How does it compare to Lay on Hands? Well, this recharges on a SHORT rest, is worth almost as much, and can be used on all targets in a 60ft range simultaneously, as a bonus action. This blows Lay on Hands out of the water.
7) Races - Half-elf, Drow, Eladrin, Tieflings Aasimar, and Humans (Variant) seem to mix well with this one. My personal recommendations?
a) Triton - Str bonus, Con bonus, and Cha bonus FINALLY works for a class. Plus you get some resistances, Swim speed, and some other cool stuff.
b) Human (NON-variant) - Get a 12 in Int, Wis, and Cha (for a +1 in Saves for each one) then max out Str/Dex and Con. All-around this will help with Bulwark much better in later levels.
I suppose my top tip for playing the most effective PDK would be to simply not play a PDK.
Cool story.