The best way to reach me is by email; My address is:
Although I do my best to respond to as much as I can, I admit that I am not able to respond to everything.
In some cases your question may already be answered on the site: e.g. tutoring, contest resource recommendations or the FAQ. If you need help with an olympiad problem, you are better off asking on a forum like AOPS. Contrary to popular belief I can't sight-solve everything!
Here are some hints:
Comments, thanks, or suggestions on my writing are always appreciated! This includes any trivial typos you find.
My replies are often terse. Please don't be offended if so. I am just trying to be efficient since I get many messages.
Proper syntax, English, capitalization, etc is appreciated. (I know some of you are not native English speakers, so I try to overlook this when I can.)
Please be patient. "Bumping" a message before I have found time to respond is likely to annoy me. I ill not respond to a non-urgent message that is bumped after less than two days.
Specific queries get faster and better responses. So "can you explain this line of your solution to USAMO 20XY/Z?" will usually be answered pretty swiftly. Conversely, "how do i geo" will get at best a link to the FAQ.
Don't be too shy! I might sound scary here, but if you have a good reason for contacting me and do so politely, then I won't mind. I am happy to help where I can.
(Examples of good requests: specific math query, something I wrote is unclear, found a typo, follow-up questions, permission requests, questions on my past experiences, etc. I'm sure there's more.)