I will be brief, otherwise there will be a wall of text. If something is unclear, ask in the comments. Share your tips!

1. The prices of many products are raised before each 11/11 sale. This is a common practice. They will drop again afterward.
2. Not all sellers offer discounts, even though this is the biggest sale of the year.
3. Three days after the 11/11 sale ends, Black Friday will begin.
4. It's unclear which sale will offer the lowest prices. See point 8 for more.
5. Be sure to use both Aliexpress coupons and seller coupons! These are what lower the price.
6. Try subscribing to the store. The seller might send you an additional coupon, as has been mentioned in other threads.
7. Sometimes a product may disappear from the sale during the event, either because it's out of stock or for other reasons. This is rare, but it's something to keep in mind.
8. Make sure to check the price history for the products you're interested in. Type "aliexpress price history", "aliexpress price tracker", or something like that in Google and check the price chart. This can help you avoid impulse purchases and give you confidence that you're getting a good deal. Regarding point 4: if a product has been on sale for a long time, you may be able to see during which sale the price was lower last year. However, this may not apply this year.