For reading, most hand histories start by first putting the round information (what is the dora, what round it is, how many tsumibou are on the table, point situation and other information that may or may not be relevant such as the number on the die or whatever). These are pretty much self explanatory. Then, you have the hand histories of each player separated, but they all follow this format:
Starting Hand: this is the tiles they first received and the base for the hand history.
Draws: This is the tiles they drew each turn. If they have an X it's because they didn't draw, meaning their turn was skipped by a pon. Of course, the dealer starts with an X because he doesn't draw, he directly discards. If it says "Pon" or "Chow" on top it's because they didn't draw it, but called it.
Discards: This is the tile they discarded in exchange for the draw exactly above it. If above the discard there is no drawn tile and there's just a black arrow, then it means they discarded the tile they just drew (tsumokiri). If it says "reach" below a discard, it means they reached discarding that tile. Other additional notes on that tile may be written below it (i.e. "North Player's Winning Tile") but everything will again be self explanatory.
Final Shape: How the hand ended up looking after all that drawing and discarding at the end of the round. Because, you know, it's so easy to lose track that it's so much more comfortable to have the final shape displayed. Other notes may be added in here, especially on top of the winning tile (such as rinshan/haitei/houtei or anything else that's not self evident by looking at the hand).
But yeah, RM's website's hand histories are a little bit confusing. But that's mainly because they are posted in a website form, and when you look at it all you see is tiles. So, let's try with one of Saki's hand histories:
Team Match, First Match, E Table. Kiyosumi Highschool Taishou, Miyanaga Saki.
Dora 7p, Kan dora 9p. Ura Dora N/A. Dice: 4
North Seat: Kiyosumi High School.
Her starting hand was:
First turn, she drew a North which she discarded. Next, she drew 4s and discarded White Dragon. After that, she drew 6s and discarded the 9s. Then, the next three turns she drew South 3p 9m which she immediately discarded upon drawing. When the fourth 4p came in, she discarded 7m. Next draw, she picked up and discarded 3s. When the red 5s came into her hand the next turn, she discarded 7p. Next turn, she drew and discarded 9s. On her next draw when she picked up 6p and got her tenpai (single wait for West) she made a kan on her four 4p and drew her winning West. Meaning her final hand was:
(Rin Shan Kai Hou)
I hope I was as detailed as possible...
For writing, you don't need to worry, once you learn how to read it, it becomes apparent on how you should write it as well. Anyway, some professional associations have workshops for learning how to write hand histories.