@somethingstellar, this is what I wrote a couple of years back. I'm repeating it here, in the hopes that it may be of some help to you:
"I have finally managed to create a high-end restaurant (self-built), which makes over 2000 simoleans net profit a day. This is my advice for maximising profitability, based on what I have learned:-
1. Hire only one of each type of employee (at least to start with) and invest in their training. In particular, get your chef to max out his skills ASAP and promote him (or her) accordingly, to keep up morale. Once his skills are at level 8, set him to cook quickly. I am not sure whether it is worth maxing out your host's and waiter's skills. They seem to do fine at a skill level of around 6/7 (mine are maxed out now, but it does not seem to have made a significant difference to their performance).
2. Buy the inspirational speech perk ASAP and use it on each employee daily. Systematically buy every other perk that will have a positive impact on the restaurant's finances - ingredient discounts, well-heeled customers, bigger tips, etc. Get the patient customers perk too, to stop your customers getting fed up and walking out when service is slow.
3. DON'T waste points on the customers-eat-faster perk (whatever it's called). It doesn't seem to have any discernable effect on turnaround and IMHO is not worth it.
4. Buy the cheapest advertising package (silver). The more expensive packages are not worth the extra cost, but you do need some advertising in order to attract enough customers to ensure a high turnover.
5. Set your mark-up to 300% - yes, really! Your customers won't mind (this is supposed to be a high-end restaurant after all).
6. As your chef's skill level increases, customise your menu by progressively removing the cheaper options and offering only the most expensive food and drinks your chef can produce. Eventually, you should offer nothing below a difficulty level of 4. Your customers won't mind or even notice the more limited choice. You can include dishes that are slightly above your chef's current skill level. Ignore the warnings. Customers will still pay. This might be a bad strategy in RL, but it works fine in the game.
7. Don't comp anything. Comping affects your ratings, but does nothing for profitability. The game is geared to make you focus on ratings, but higher ratings do not necessarily mean better profits (in fact, I have seen no connection between higher ratings and profitability at all, but that might just be me). If it is profitability that you want, then it is on profitability that you need to focus. There is none of this 'do the right thing and the profits will surely follow' that you get in RL. This is not RL.
8. Now for the crunch: You must stay open late, because the majority of your customers will arrive in the evening and your profitability depends on how many customers you serve. Your employees are only equipped to work for 12 hours before their morale suffers (talk about exploitation!), so don't open until noon, then you can stay open until midnight. Your employees won't mind the late hours, but your managing sim will get tired, so make sure there is somewhere private for them to take an afternoon nap when things are quiet. Or let different household members take shifts.
9. Make sure you have enough tables (I had ten). The secret lies in the number of individual tables, not the amount of seating generally, so most of your tables should be two-seaters, since customers will generally arrive in pairs and these tables will fill up first. Put them closest to the chef's station for quicker service and make sure that there is plenty of space to walk around them so that the area does not get too congested if/when your customers decide to play musical chairs.
10. Don't enlarge your staff complement too much, or too quickly. I have tried having one chef and I have tried having two. Having two chefs at a pay-grade of 5 was hugely expensive (especially when you include the training costs) and, even with maxed-out skills and set to cook quickly, service speed did not improve all that much - at any rate, not enough to warrant the added expense. My current restaurant has only one chef and he seems to manage perfectly well. But I do have the patient customers perk too.
11. I have not decided yet whether it is better to have one or two waiters. I managed perfectly well with only one waiter for a while, but she has started slacking off and it might be time to replace her with someone new and more motivated, so I have brought in a second, more junior waiter to start training and will see how things go from there. If you only have one waiter, though, your managing sim needs to help out. Apart from welcoming guests and checking on tables, there is only one thing that they can usefully do and that is to clear tables. Make them do this.
12. One last tip - hire the youngest staff you can get, especially as hosts and waiters (and especially if you have aging allowed, which I don't at the moment). For one thing, they move faster and (unless it's my imagination) they seem to tire less quickly. For another thing, if you have aging allowed, they will live longer and therefore offer better value for your investment in their training."
A couple of extra things I have learned since writing the above: Don't put in music. You don't want customers standing around dancing. And you probably shouldn't put a bar in either. I think some of the worst problems that came from doing that have probably been ironed out by now, but it's probably best to avoid it in any case. And good luck!
