You have to try to remember that this is a game about parks, not carnivles, if you pack the rides in too tightly...... you'll be sorry.
This ones hard, but cool. put a bear or elephant in a little pool of water so he waves at you, the pull the land up underneath him really fast. sometimes he'll fall through the bottom of the map, but sometimes he'll get stuck so it'll look like you have caged amimals in underground veiw, the peeps have x-ry vision so the effect will get them, great for zoos.
Stuck under 3,000 guests? try theming. I find it next to impossible to get much over 2,500 with out a theme, the guests abosolutly HATE a themeless park.
The low-down on security guards: they CAN be useful, but only if you make them, you have to make them patrol a trouble area, because the way they work is this: Vandals don't vandalise if a security guard is present, they don't get caught, they just DON'T VANDALISE!. Therefore, if they don't patrol, a set area, they will wander off, and the vandals will keep on vandalising.