Okay, first I would like to commend the OP for the patience displayed for the PuG groups as most people nowadays are all "Me me me, now now now" and basically giving new player zero chance to learn. With that said, however, here is a few tips which you can be a successful PuG leader without doing anything fancy. Now, before I do, the disclaimer I am going to say is: This may not work on all occasion as there are "exceptions" who are just creatures of pure spite/ignorance/stubborn/apathetic to be convinced to succeed. Also, these tips works best when loot rules are Master Looter and the setting is an Operation.
1. Before the group even start pulling the first trash pack, make this one single point clear: "IF YOU WANT LOOT, THEN DON'T DO STUPID STUFF". Then outline what you consider as "stupid stuff" so everyone is clear. This will generally discourage "Gung-ho" DPS trying to pad their non-existing meters. Or tanks/heals trying to show off their ego by biting off more than they can handle.
2. When explaining fights, treat your audience like idiots. I mean it. Explain the mechanic in the most simplistic way possible. Keep your sentences short, clear and concise. Don't EVER type out the entire fight in one single wall of text. Chances are people will just risk winging it than try to read through it. After done explaining, ask if the new people understood what you said and FORCE them to answer you ("If you don't answer in any way, I won't pull/we won't start). Reason behind this is, people have very short attention span online. This applies to all ages, all ethnicity and genders. If you can't explain the needed mechanic in 1-2 min, chances are your audience will space you out. Also not everyone has English as their dominant language.
3. Tying into #2 from above. With each boss ALWAYS ask your group if everyone understands the fight. Remind your group that it is OKAY to NOT know the fight, and that speaking up will not get them kicked. Most of the people try to "blend" in and pretend that they know what they are doing because they had experienced situation where they spoke up and it affected them negatively. Generally, when I say I won't kick people just because they don't know the fight, I usually get 4-5 people say they don't immediately after. You can further reinforce #3 with elements from #1 saying "If I catch you screwing up on the most obvious mechanic and you didn't say you were new; you don't get loot"
4. Always verbally reward your group to keep your group's morale high. Humans are animals and animals like to be rewarded. If your group performs brilliantly, let them know that, a group with high morale are more likely to focus more and perform better. If they are not, tell them that too. I prefer to point out mistakes as bluntly as possible and not sugarcoat stuff. That way your group at least know you mean business and in charge and that you are not going to willingly lead them to wipe fest.
5. (Bonus) Know tips and tricks of other classes that are not apparent in "everyday" use, particularly new players who are just entering mass group play situations. For examples, some Commandos do not know they have a in-combat rez, interrupt ability (Distracting round) or a CC (Concussive Round) or Guardians who do know they can leap to FRIENDLY targets via Guardian Leap, Shadow/Scoundrels can do in-combat stealth+normal rez, Sages can pull friendly targets to their position via Rescue, Sentinels not knowing about Rebuke/Pacify/Guarded by the Force/ Inspiration/Transcendence/Valorous Call or Gunslingers not knowing about Flourish Shots and Scrambling Field (Raid wide 10m 30% dmg reduction "bubble").
By following these 5 points above, I had led countless seemingly hopeless PuGs to success and had gotten numerous "Hey good raid leading, that was my first time clearing [insert Operation here]" or similar whispers. This has been always been my personal motto "If you can't carry the team to success by yourself, then you are simply not good enough".