So, I'm trying to create a park with no CS (as I usually do) and I wanted to make a custom catwalk for my Batman clone. Does anyone have any good tips/cheats on how to make one and make it look realistic? Thanks! 

Hi, I'm assuming you're working in RCT3 (That's where no-cs is most commonly found), I have a few ideas for that but I need to know what kind of look you're going for.

Yes, I am working with RCT3... I just wanted the ride to look realistic. All I really need is a catwalk design for a B&M inverted. Thanks!

Hmm..... Well... You may need CS to make catwalks for an invert... at least if you want them yo look realistic anyways. If you're doing the lift hill you'll definitely need CS. Let me know if you'd like links to some sets.

Not really sure exactly how to build one, I would suggest use fences, base blocks and different wall pieces

There is that video that might help you a lot, especially for how to make the fences:
https://www.youtube.com/watch?v=grqXQR5WBFo

For the rest, I found a slighty difficult way to make the catwalk if you really want it under the track. In this case, I suggest you to find a roof that would work well as a catwalk (the default roof might work). Then, lower a bit the land under the track and place the roof under the track. After that, elevate the land at its initial level, you'll see that the roof piece will rise itself too. Check my attachment to see how it works:
   

If you want the catwalk to the side of the lift, you should use paths. I think this is the best way to make catwalks on the side.

Finally, you might try to remove the supports with custom supports (made with vanilla objects) and/or foliage and other kind of scenery.

This is the best tips I can give you for now. If I find others ways to make catwalks, I'll let you know in this thread.

Here are some videos you may want to check out
https://youtu.be/grqXQR5WBFo
https://youtu.be/txEG2xrkEKE
https://youtu.be/e1KMrUHr_sw