Do clumps of solo quests. Try to stay in the blue to orange range.
It really is that easy. Quests will come in clumps, with several contacts sending you into the same area. Get every quest you can in an area, then head out and do three to six at a time. When your bags are full of loot, come back, turn in quests, then do another batch. Group if it is convenient, but you can level very quickly without it, and waiting for a group is the part that slows you down. (You may want to make an exception to finish your epic books, and those are the easiest groups to find.) If you have few or increasingly green/gray quests in an area, move to the next area; you should have a quest telling you to talk to someone there.
Say that you are a new player in Bree-land. In Staddle, you can get quests to defeat bugs in the swamp, to get fennel seeds from bugs, to defeat the spiders near the bugs, to defeat the goblins near the bugs, to defeat boars in the nearby woods, and to talk to the hobbits near the guy on the fennel seed quest. Those hobbits will give you quests to defeat bears near the boars, pick flowers near the bears, and fight brigands just past the flowers, along with some running around the area and picking more flowers. Do all those, then you will be sent into Bree-town, with a half-dozen quests in the Barrow Downs, and you can do the half-dozen quests around Adso’s camp along the way.
The goal is to stack objectives. Get two people to send you to the same town. You can have “kill 10 boars,” “kill 16 boars,” and “get 12 chunks of boar meat” at the same time. It helps to be on a second character, so you have already done your Explorer stuff and can just Achieve now that you know what contacts give what, but your first character can zip along as quickly as you like.
As a solo Minstrel, I went from 29 to 32 on Thursday (and not “29.85 to 32.02”). I also worked and played other characters that day, so it was not a catass binge. If you are going into town and see fewer than three rings, you are going slowly.
There is nothing wrong with going slowly and stopping to smell the flowers. My first character has completed almost every quest in the game, with almost all the deeds except those requiring hours of grinding at level 50 (and quite a few of those). But if you feel like things are slow and grindy, that is a factor of how you are playing the game, not the leveling pace the game offers. You can run around the grouping wall and zip to the next stack of quests. You may not have solved all the problems in that town, but don’t worry: nothing you do makes a difference in the game world, so those monsters will always plague the town and those NPCs will always have the same problems.