Like CB said, place a toilet next to your exits, especially on the high nausea rated rides. And don't forget to open the toilets! I didn't do this the first time around and boy! Did I have a mess on my hands!

Use the advanced mode camera. It's a little more difficult to use, but you'll master it. You can do things with this camera that other cameras won't allow. This is the ONLY camera worth using. The others are not nearly as good.
Find the cheat codes online. Copy them, and print them. There's camera controls (hop on a peep, for example), and other goodies. Check 'em out right away.
If you're intent on making videos, Fraps works superbly, and in my experience, better than the built-in capture routine. You can capture the sound for one thing. Whats a coaster without the roar?
If you're working in a scenario, try not to ride the rides until you get a positive cash flow. Then enjoy it. This is your reward for success, so don't be rewarding yourself until you succeed. A positive cash flow is success, so start riding rides when you get that far.
If you're working in scenario mode, pay back your loans! That interest costs you monthly and annually. Pay down your loan when you have sufficient rate of income, and watch the rate climb faster! Pretty soon you'll be making coasters without loans.
Before playing a scenario, examine the scenario builder. Examine it thoroughly! You'll learn a lot about what to expect, and how to get bonuses in the form of cash. There are bonuses for things that are not explained elsewhere. Find out what these bonuses are.
Create your own scen to learn what to charge for rides. I'll attach a scen I've made for you to find out what to charge. Play with the settings in the editor to see what happens. You'll find out what works, and what makes a scen damn near impossible.
Don't... and I mean don't, have a lot of balloon vendors. Balloons are cool, but if you hop aboard a peep for viewing and taking screen shots or making a video, those balloons are in the way. Also, they hurt your frame rates. So, look for a good balance. Once there's sufficient balloons to make the park look fun, shut down or even remove your balloon vendors. Sell something else instead.
Park funding -- the road to economic success in scenarios
Most of your money will come from rides. At least half will. The other half comes from food and drink sales, and souvenirs and toys. At first, spend money that will earn you money. Don't be prettying up your park right off. Sell! Spend money to make money. You can pretty it up shortly thereafter.
Coaster Building 101 --
COUNT! Count how many ramp ups. That will tell you how many down ramps you'll need. COUNT. Count the horizontals. That will tell you how many you need to go back to the beginning of the ride. COUNT! Write down the numbers if you have trouble remembering. This makes makes designing much easier. COUNT! It's really all about math. Once you start counting, coaster building becomes a lot easier (but it's still tough).
Coaster Building 102 --
Find a coaster you like, and build it over and over. You have plenty of time to learn the other coasters. Learn 'em one at a time, and MASTER them, don't just dabble. Keep trying to get that level 7 coaster, or as high as you can get. Then, move on to another coaster. WHat you learned frojm the previous one can be applied to the second. Stay organized.
Coaster building 103 --
You can save the coasters you built for use in other scens or sandbox. But note that you can only save the coaster and the entrances/exits. You cannot save the terrain under it, if you've made a mountain to run it through.
Save your games!
Save even your smallest attempts at learning the game. If you forget something, you can go back to it for reminders. Then when you feel fluent, then remove these saved games.
Run the tutorials more than once. Do 'em twice. Perhaps even three times. You'll learn better this way. And don't forget to sleep on it. Sleeping helps learning -- that's a newly discovered scientific fact.
On terrain shaping: Of all the tools available, the most important ones are leveling. Learn all that you can do. This will save you time in the future. THere's some very powerful tools here. Learn how the leveling works. There's many methods, and there's a reason for all of them. Learn these, and you'll make better looking parks. Flat is dull!
IF YOU ARE MAKING VIDEOS, defrag your disk immediately after recording, then once again after you made the final product. For some reason, video making really trashes your disk. So, keep it clean, and it'll be mean.
Erm... more to come as I think of them.
If you have some tips, post 'em in this thread.
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Okay... here's the basic scenario I made. This goes in My Documents/RCT3/Start New Scenarios. Open it and take a look at all the numbers. Then take it for a test spin. When your'e done, change some of the parameters, and take it for another drive. NOTE: If you save your game after you've built a little, name it differently. This helps you keep track of things.
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