Are there any restrictions I should be aware of when adding words to the dictionary?

I added 肿么了 today, which is internet slang for 怎么了, and I probably wouldn't put that in a dictionary, if I were the editor, but it is still a word I want to remember. Is it OK?

How about if I added the Baidu Mythical Creatures (e.g. 草涅马)?
http://en.wikipedia.org/wiki/Baidu_10_Mythical_Creatures

And lastly, I think knowing the twenty (or so) subway stations between my apartment and my university would be useful, so can I add them?

I can simply not find any guidelines that have to do with which words are appropriate to add. Do any exist?

It would be awesome to have more internet slang on here--and a big heck yeah to the mythical creatures. Really, so long as you follow the style-guide below, you can add whatever you want, as long you make sure it actually is or has been used.
http://www.skritter.com/style_guide

I has been adding ramdomly since I started. I thought they would ended up in my personal database somewhere.

How could I go back and fix them?

They will probably get fixed in the course of balling. If you see one, you can always submit a definition correction to help rectify the style.

Awesome, thinks.

赶上 is in the Skritter dictionary already. Can you describe any error messages you're getting and what steps you're taking to input it?

You can't change the tone yourself, although if you submitted a reading correction, Evan would consider altering the tone to allow both the neutral tone and the full tone, depending on how standard each option is.

You still didn't describe any specifics of how you're trying to do it, only what you're trying to do. I will guess. For the custom definition, you can use any of these three normal custom definition editing methods:

A) In the iOS app, when studying the word, tap the top prompt area, tap the definition edit pencil, and customize.

B) On the web study page, when studying the word, click on the definition and customize.

C) Anywhere on the website, click on the word to get the word popup, then click the edit definition pencil and customize.

This process will not work:

F) While editing or adding words to a list, rewriting the pinyin and definition from within the list editor.

Instead of attempting method F, save the list (stop editing it), then while viewing its contents, click on the word to get the word popup as in method C.