1. Environment: Your world has to make the player want to explore the level, Good layout and texturing essential.

2. Objects: Think very carefully before placing objects, remember, an Egyptian statue can look very out of place in a Greek setting, or vice versa. Place objects only that are needed or would add effect, objects just thrown about all over the place don't have any effect on the player.

3. Size: Don't make your levels too big, or the player will feel too overwhelmed at the size to start exploring. Remember, Lara is supposed to visit archeological sites, not countries. But don't make your levels too small, or else all the challenge is taken away.

4. Originality: Now we are reaching the 400 level mark, the levels you make have to be original, so try to spend at least 2 hours thinking up a strong plot before setting to work making the level. Writing a script helps.

5. Reality Check: Remember, Lara is supposed to be human, don't go placing her on the sun!. Make sure your ideas don't get too fanciful, but try to make them interestingly different instead, again going back to the point about originality.

6. Lighting: This is really one of the things that can make you think 'wow, I wanna play that' or 'What is this?'. Even bad texturing can be masked by good lighting, although this is not recommended. Try and make use of fog bulbs and effect lights, and the shadow (anti) light can have a good effect too. Also, when you place an object, change the tint by using the colour controls on the object panel, if you use 128 128 128 in a 16 16 16 ambient set room it'll look very out of place.

7. Outfits: Think hard about this, don't just go for something you think would be 'cool', try and actually think 'Would she where this here?' and 'Why?'. Placing Lara on the Antartics wearing a bikini might look "hot", but it's not very realistic.

8. WADs: Okay, so this is sorta samey as the object one, but this actually talks more about choosing objects than placing them. Think about your level idea (revert back to your script), try to get a visual of what you want it to look like in the end, then decide what objects would be good. It doesn't matter that much, because you can just change the WAD whenever you like, but it all saves time. Also watch out for those texture limits.

9. Publicity: Ok, ok, this isn't specifically about level design, but try to design some artwork to publicize your work, whether it be banners, screenshots, or just telling people about it. You don't want to have spent 2 months on a level and then no one knows about it or wants to play it, do you?

10. Test: This is so unbelievably necessary, test every section again and again, there is nothing worse than releasing a level with bugs in, not only will it put people off the level but off all future levels you may make. Try to get a friend to test it, you can't do it by yourself, because you know where everything is and what to do, you don't need to 'explore' which other players will.

11. SAVE: This can't be said enough: save very often! It's really frustrating when you worked on your level for hours, forgot to save, and then your PC crashes and losing a lot of sweat and tears. Also, when saving your project, don't overwrite anything, but save it on a new filename every time.

people who contributed to these designer tips:
Kiopo
DriberBallZ