To be honest BrtnBoarder, the advice youre giving is just generalistic things that I'm sure dirk already is aware of. I think he wants more specific or in depth input, not just the cliche space your rides, have bathrooms etc. stuff. Especially since all of that stuff is much less important when speaking of a truly great RCT park. The main things that can make a park great are archy, coordination and planning, theming(obviously), good ride layouts/interaction, and success at achieving the intended affect ie realism for a realistic park or creativity and originality for a fantasy park.
Archy- Along with the obvious that youre archy should be aesthitically pleasing, you must ensure three other things. Consistency in architectural style per each area (in other words avoid having randomly constructed buildings that dont look like they have anything to do with each other aside from color), always ensure that you have a certain level of architectural variety while maintaining the consistency, and lastly always ensure that your archy possesses funcionality and reason. Every building should serve a purpose, and every piece if every building should add to the building and provide added quality/usability/aesthetics to the building of which it is a part of. Follow the golden rule of archy-The structure should be better than the sum of its parts.
Coordination and planning-Self explanatory really. Ensure that every part of your park is well planned and makes sense. While you don't have to neccessarily have premeditated everything (many great areas of excellent rct2 parks started as somehthing else), at least refine what you build to create a sense of coordination and organization. Also, pay attention to details and come up with clever means of arranging your park/coasters/paths etc in order to give a sense of extroardinary refinement to your park, which in turn will greatly add to the quality of the park.
Theming- Try to come up with original themes, or an original way of creating a common theme. Or if you are going for a deeply realistic feel (ie a disney based park with a tomorrowland), ensure that you get the theme across well with every section of the area adding to the theme's development, as this will make even a theme as common as tomorrowland or jungle become a sophisticated area that will add to the park being great.
Ride layouts/interaction- If you are going for a realistic park, make rides that have believable layouts with accurate realistic supports as well. Also, try to add realistic details to the rides such as transfer acts, believable stations, sophisticated foliage and landscaping, and solid entry/exit lines. Also, if you desire even further realism, consider mimicking rides (ie make a woodie that goes underground numerous times to be very similar to Voyage, which will make the ride more believable and exciting). Also, attempt to duplicate the atmospheres of real parks such as IoA, Disneyland, or any other park with a great atmosphere, if you successfully add in the details and surroundings that can be found in these real parks your park will become even greater and more believable.
Realism-Already covered above for the most part. Use your knowledge of rollercoasters and parks to accurately create a realistic park that remains interesting and fun to look at. Attempt to have realistic pathing, foliage, and buildings that are detailed and refined to the furthest extent, but still not overdone.
Also, it helps to view other great parks. For WWS.com, I'd reccomend checking out SupremeScreamer's parks as well as X250's creations. SS's are extremely realistic, while X's are extremely creative and well made but may be a bit less realistic. Also, I'd reccomend that you look at some of the parks on nedesigns.com, the spotlights on ne.com are unquestionably some of the best parks available for rct. Specifically, I'd recommend checking out Rivers of Babylon by SACoasterFreak, Euroscape by Butterfinger, Six Flags Worlds of Excitement by Phatage, Isole Calabria by Turtle, and Islands of Enchantment by Artist. These can all be found in the spotlights and runnerups links at ne.com. There are many other great examples of quality realistic parks there as well. Hopefully I have been of assistance to you. [:D]