Once you have stayed in accommodation you should, where possible leave reviews. Reviews are very important for people to be able to make a judgement on whether or not they wish to stay in said accommodation and can be important feedback for the accommodation owners.
When writing a review there are often a number of places you can post it. It may be that you leave a review with the accommodation provider either on their website, in person or in a review book or you can often post reviews on third party websites such as Trip Advisor.
You should always be honest and fair in your review and try to leave details of positive or negative feedback. It is equally important to leave feedback for good or bad stays to give a true reflection of the accommodation. If you encountered an issue when staying somewhere, report it first to the owners and allow them time to rectify the issue. If it was dealt with quickly and resolved then be sure to mention this in your review.