Writing in binary is actually very simple, at least if you want to do the basics (although punctuation can be pretty confusing). Letters and numbers, though, all follow fairly simple rules.
It's only 2:14 and the night is young, so I figure I might as well post them, now.
Everything:
Everything (letter, number, punctuation mark...ever ASCII character, in general) consists of 8 bits. That is, there are 8 numbers (all of which are 1's or 0's). Space (" ") is the easiest one to remember. It's 00000000.
Capital Letters:
All capital letters start with 01. After that, you must find the number that corresponds to each letter (e.g.: A=1, B=2, C=3, etc). You then convert that number to binary. Keeping in mind that each letter is 8 bits long, you write 01, followed by X 0s, and then the binary representation of the letter's number. X is determined by however many 0s you need to have a total of 8 bits. For example, 'A' = 01000001, 'B' = 01000010, and so on. Get it? Got it? Good.
Lower Case Letters:
These are pretty much the same as capital letters, except that they start with 011 instead of 01. So, for instance, 'a' = 01100001, 'b' = 01100010, and so on. Not too complicated.
Numbers:
These are a lot like lower case letters, actually, but with an extra 0 at the beginning. All digits (numbers 0-9, since all numbers greater than 9 are composed of digits, so there's no binary representation for them, specifically) start with 0011. This is then followed by X 0s (see definition of X, above), followed by the binary representation of that number. Following this pattern, '0' = 00110000, '1' = 00110001, '2' = 00110010, continuing on like that.
Hope you enjoy binarying. Remember: There are 10 types of people in this world. Those who know binary, and those who don't.