How can you check on assisted living places?

ALF are not regulated in the way that Nursing Homes and SNF and rehabs are. They have few rules. They basically are their own entities with staffs, meals, and activities. They are not regulated as to costs and most are private pay.
You should call facilities in your area and ask how to tour and interview with them.Do know it is unlikely they will ever let you alone again unless you say you are flat out BROKE. But they will give the information and answer questions and give you tours. Start with your list of questions for them. Tell them a brief bio for yourself. You will find facilities for your area listed online.
Many like the services of such companies as A Place For Mom. My brother and his ex were well served by them when he was looking for placement for his friend. They did not pay for the services but the company received a payment from the facility that was eventually chosen for care. Others feel that you are contacted too often by them once you register. Do know that they will ask personal questions such as your assets, your ability to pay months costs and etc. That's a part of the deal if you use them. But they often are familiar with what places might be a better fit for you than others, and why.

https://www.medicare.gov/care-compare/?providerType=NursingHome&redirect=true