What services should be enabled to use the reporting services?

During installation of SQL SERVER REPORTING SERVICES, installed create few windows services at server level. These services are required to be in start state. Services activates the SSRS instance and reporting services. You will find the services at Start->RUN->Services.msc.

Another dialogue box will be opened and you can check for

Important point to note here is from which user services are running. You should always use a facelessID or different account or password less account so that you do not run into ID lock issue. Frequent password changes are not good practice for the user.