Your listing’s ranking is affected by your responsiveness to reservation requests. Your listing will state your average response time – aim for within an hour:
Airbnb encourage guests to contact multiple hosts. You are likely not the only host being contacted about a potential guest’s booking. Being the first to respond will give you a definitive head-start on winning the booking with all other things being equal.
The easiest way to ensure you’re notified of reservation requests immediately as they come though is to download the Airbnb app for your smartphone: