I know this is an old post, but for anyone who stumbles across it like I did last night, here are some tips:
Play a town you've played in before and can deal with for the rest of the challenge. Of course, if you just follow the general idea of the challenge (no cheats, 10 gens) then it doesn't matter so much because you can move from town to town when you get bored. However, if you do choose to stay true to the original rules, I would advise picking a town such as Sunset Valley or Riverview. Bridgeport, where my main legacy is stationed, is not a smart choice. Being as it's a city, it can take my sims up to 4 hours to get to school and even longer if they're coming home from a night out on the town. Also, the game lags a LOT and the biggest lot I could find was maybe a 30x30.
Vampires! Again, my main legacy has been a vampire family from day one. But there are ups and downs to this occult. Your first generation of vampires (founders) are just like normal sims sans the fact that they can't really go outside. However, their vampire babies basically become mutants. This may sound cool (once I explain) but after a year of playing through 5 generations, life gets boring REALLY fast. These 'mutants' are great for skill leveling because in the amount of time it takes for a human sim to level up one point, these vampire mutants are at least level 5. Within an afternoon I can teach my sims to drive, max their athletic skill, do their homework, max their guitar skill, and still have time to become the best diver there is. So what's so bad about fast leveling? Well, besides the fact that your sims will soon be out of activities, interactive jobs introduced through Ambitions tend to be harder to reach the top of. On the plus side, homework doesn't take long to complete. Which leads me to my next point...
Know your job If you know your heir is going to grow up to be a scientist, get that gardening skill started early on! On the other side of the spectrum, if you know your sim will end up in an interactive job such as firefighting, hold off on leveling skills before getting a job because this will affect your ability to climb the ladders quickly.
Bonehilda isn't necessarily a good thing... This is a personal opinion here, but I would stay away from Bonehilda. While it sounds like a great idea at first, she doesn't really do much. Yes, she will take care of the trash and set out meals (which gets annoying when you're playing a bunch of vampires!), but otherwise she's useless--especially when it comes to babies and toddlers. A normal maid or butler will attend to a crying infant, but Bonehilda just stands at the crib until another sim comes and takes care of the screaming child.
Founder Traits The workaholic and neat traits are good options for your founder because then you can work from home (earning more money and getting you to the top faster), and you have the option to clean the whole house, making up for the I'm-too-poor-to-fund-a-maid problem.
Fertility Treatment Yes, everyone wants to have this reward, but be careful with it! If you dole it out to every sim, the amount of twins you'll end up having is astounding! Plus, always having multiples gets boring.
Paint! Write! Do something! It's always good to choose a hobby or activity your sim can benefit financially from as well. Genius sims can solve problems on the computer for money, you can paint, write stories, play for tips, garden, etc. This also helps increase the cash flow early on.
Partners As soon as you get a good amount of money and all your basic house needs are taken care of, consider becoming a partner in a business downtown. Every week you'll be earning at least $1500 just by being a partner! And, the more you buy, the more you get. Eventually, you can be making at least $50000 a week if you invest and completely buy out a few places around town.
It's not always about the money Once the money starts rolling in, you may think this means you're required to buy the more expensive items. But don't be fooled--some items give just as many benefits as the costlier versions.
Don't give in! Even though it's hard at first, refrain from using any money cheats (or cheats in general). Your sim will survive, believe it or not, no matter how much money they are/are not making. Just think of how far you'll have come in a generation of playing! It's not as bad as it seems, so don't throw away the game because you were desperate.
Legacies can be so much fun if you just have the patience. You can always take it a step further and create stories for others, hold polls for new heirs, or throw in extra requirements like not being able to pick the same LTW twice. Either way, legacies are a great way to get to know your sims!