Depends on the Vanguard quest you farm, really. Farmer Hammet is among the easiest to farm because you get the baddies right outside Foible's Fair so you can just rezone and kill them non-stop.
It also helps if you have a pet and the bonus imp (you also get a lvl 20 pet in the process and they're extra help). Well, the pet mostly as bait.
What's your secondary? /R is the most widely used, mainly for Troll Unguent.
What's your main weapon? People usually go for sword because of Sever+Gash which gives Bleeding and Deep Wound, and it's easy to get yourself a decent 10-14 sword crafted by Ayala in Ascalon. Remember to also customize it.
Make sure you got all the +7 armor pieces. The 50 iris flowers can be farmed fastest outside Ashford Abbey (get out the gate, turn right, go down the hill using Alt to spot flower, pick up, map to Abbey, repeat).
If you got some money, buy 2 Charr salvage kits and some runes/insignia and add to your armor. Runes: +1 strength, +1 sword, and vigor are most desirable, then optionally one absorption and vitae for any empty spot. Insignia: if you're gonna farm the elementalists in Farmer Hamnet then Dreadnought; Sentry or Survivor are also good. Prices: 8-9k for each kit, 4-5k for Vigor, 1k for Strength, 2k for Sword, Vitae and Dreadnought should be very cheap (100-200g), 600-700g for Stalwart and Survivor.
Make sure you get a shield with Strength requirement or if requiring Tactics, very low req (no higher than 3, maybe 5). Remember that any drop shield will give you 8 AL even if you don't meet requirement, and the quest Unsettling Rumors gives a shield with 9 total AL and no requirement.
Get all the quest rewards if you haven't already, the total XP is nothing to sneeze at.
Speaking of Tactics vs Strength, put as much as possible into Strength and Sword, with leftovers in Wilderness Survival for Unguent. Only put the absolute drags into Tactics. Don't bother with the pet if you don't want it, it does feeble damage and you can get a lvl 20 pet in Post anytime with minimal effort.
Skills: Frenzy, Sever Artery, Gash, Troll Unguent, Healing Signet. Add Res Signet if you play with someone else. Comfort Animal is optional.