sure you register on BA Shopping and it then tracks your subsequent purchases.

Remember the accommodation sites like Booking.Com and Hotel.com all only grab you the actual Avios 90-120dsy after your hotel stay..

With Hotel.com you can credits for staying but these naturally come at less Avios points.

Beware of Hotels.com though. they cancelled my account somehow and I couldn't recover their mistake with a shedload of nights owing!

Avios points Vs Trivago vs booking direct, its a price point only you can reserve.

Hope this and my experience helps

SteveG