Heat symptoms?

Willow is turning 8 months old and I'm wondering what symptoms I should be looking for for her first heat cycle. I always had boys before her and have NO idea what to look for or expect. She's my first girl. About how old will she be for it? What warning signs, if any, are there? How long does it last? Besides diapers, is there anything I need to buy to get ready? What else do I need to know that I'm not even asking?

She's an only dog and we crate her when we're not home. I know those are both good things but am lost on anything beyond that 🤷‍♀️

Here's a cute picture of Willow as a thank you for your advice!

https://preview.redd.it/tgru6ifhjpfe1.jpg?width=3000&format=pjpg&auto=webp&s=5f8ab672a40073961ec309283920705e9f0d2fcb