TL;DR version: When I go into an area I've not been to with the current character, I look at everything. It's really that simple.

Look for areas that have a lot of unique mobs, different names. Right away I think of the planar sanctum and the monks monastery. There are a bunch of different named mages in the sanctum, and every monk in the monastery has a different name. Stuff like that adds up. Look for them in EVERY area you go to. If you're in aldevari, look at gralan, the other duergar, the 4 different knights, the elf mage, the 2 different bodyguards, the princess, olgakar(fuck you olgakar!), sutton, martain, soothsayer, young elf and older elf, and I'm sure I'm missing a few. And that's just aldevari! Those obsevations might not be worth much, but they add up. Think about shoppies. With any new char, when I enter a new city I do my "rounds" and look at all the shoppies or any other unique mobs. The other things to look at, anything in a room. Look at every single sign. Areas tend to have something in the first room of the main area entrance to show the area author/area name/ect. Look at all of those. In hometowns there are healers and pits, look at all of them, all the fountains, all the statues, ANYTHING AND EVERYTHING. Look at it or examine it. Remember the hidden stuff to look at, right away I think of the violet woodland area south of galadon. There's a LOT of things to look at in that area, I don't want to give too much detail because of quests and all. Upper cragstone where, where the gems are in the cracks holes crevices, or back in the planar sanctum the room description containers with all those wands, stuff like that. That's all worth observation. These aren't worth as much as the big ones like trothon or organia, but there's a LOT of other areas and they all add up. Ohh yea, some rooms I think it's good to do a "look all" and look in all directions. I have no data or evidence to back this up, but I think if the imms put in the effort to make special descriptions for looking different directions, I think they would also spend the time to make them worth a little bit of observation experience. Like areas with hidden up exits that go up trees, or on top of a monastery or cabin. I bet those places have quite a nice view if you look around ;) Again, though I strongly believe it's true I have no real data to back it up.

Now, the deciding factor is, how much of this stuff do you know, and how fast are you at it. Some people look at the workload and throw up their hands yelling "hell no." Other people already know the areas well enough that they can explore each one in a 2-12 minutes each depending on the areas. But then people complain about all the damn sleeping waiting for movement points to refresh. When i'm under lvl 11, I can go explore an area and then wait for movement to refresh while I watch netflix/empty the dishwasher/put my cloths in the wash or dry/check some news sites/work on a role or description/ect. Then my moves are full and I go explore somewhere else. Repeat. I do that kind of stuff without thinking, because when I make a character I'm typically running around picking up stuff that's all over(and there's usually shit ALL OVER the place) and selling it because money payz da billz :) I tend to have at least 50 gold by the time i'm lvl 10.

If I really wanted to maximize how much I could farm, I would do something like this: Academy, galdon, kobold warren, eastern road, blackclaw, aldevari, by now I'm lvl 3 at least not worried about gibberlings and do violet woodlands and silverwood, modular monastery, upper cragstone, tir-talath, voralian, loch grynmear, akan and stones embrace, (NOTE I forgot to mention recal makes this easier), dagdan, halfling lands, copeham inn, eternal star inn... continue that with all the "easy" areas and you'll have a pretty good amount. You should be high enough lvl by then to get through the shadow grove and explore HToS which is worth(I hate saying this because part of me thinks every time someone says it on a forum they lessen it a little bit each time, yeah yeah paranoia yeah yeah) a lot. If you have the patience, the hamsah docks are worth a LOT(enter same statement I maid about HToS) but you have to be lvl 11 at least and 1 week in game is a long time to wait and run to each boat when they're there.

It takes me 2-3 minutes tops to sweep each one of those areas as well as many more. And there tends to be a lot of stuff people just don't notice. There are items you can go and pick up as a lvl 1(not in far off areas either) with absolutely no risk involved, and go sell them for over two gold a pop. If you take the time and explore, you'll find stuff. Simple as that. I've played for a long time and I remember where stuff is, sort of. That's how I can go look at a million things in a few minutes.

I usually don't go out of my way to rack up the exp, and I tend to end up with around 8k observe by lvl 25 WITHOUT TRYING. WHen I do try, I get over 15k observe by lvl 20, and without hardly expending any extra effort, just remember to look when I'm in the area.

If you want to talk more specifics, PM me any questions you have.