To determine which size watch strap you should get, you need to measure the strap length and lug width on your watch. Find out how here - and get the perfect fitting strap for your favourite timepiece.
There is no universal answer to how tight a watch strap should be as it all comes down to personal preference. That being said, your watch should be comfortable and secure, and a strap that is too tight (or too loose) isn't. Find out how to get the perfect fit here.