Achieving Acheivements
If you go into kingdom mode, and check out the list of acheivements, you can get an idea of which ones you want to attain short-term, and which ones you need to work on long-term. If you specifically set out to attain specific achievements, for example, Eggcellet (throw 150 eggs at people in the stocks), you should choose a quest where you are playing your monarch. Then, while you are not doing quest related tasks or daily requirements, you can send a sim to the stocks, then stand there and throw eggs at them until the guy lets him out again. (Before he has a chance to head home, JUST as he gets out of the stocks, send him again to repeat the process). Do this until you are getting behind on your quest, or need to do your daily requirements again. I keep a tally so I know where I'm up to and how much I can fit in. To have more free time inbetween quest activities, annex Ticktop. You can work on one or two of the achievements at a time.
Or alternatively, you could work on as many as can be completed by one hero, and go for a balanced approach; that is, (if you are the monarch again), throw 5 eggs, throw 5 tomatoes, have a couple of games of Kingball, have a couple of swordfights, hear some petitions. Try to pass an edict every day and you won't have too much trouble getting edict addict, or enough edicts. Do a little bit of everything every day.
If you want to start fresh and do the achievements again, you can move the Medieval Sims folder OUT of the Electronic Arts folder (in My Documents) and put it somewhere else (this will keep your current saves). When you run the game again, it will create a new folder, and a brand new game. If you want your old saves back, move the new folder out, and move the old one back in.