Get a book written by a good writer. The Manning Press In Action books are good because they are not manuals, they are tutorials that also cover the important details.

Read with a highlighter.

1. Read entire paragraph.
2. Find shortest phrase that summarises paragraph.
3. Highlight it.
4. Read entire paragraph again.
5. Read highlighted summary.
6. Move to next paragraph.
7. Go to 1.

If it looks like below, it should be easier to remember:

1. Read entire paragraph.
2. Find shortest phrase that summarises paragraph.
3. Highlight it.
4. Read entire paragraph again.
5. Read highlighted summary.
6. Move to next paragraph.
7. Go to 1.