Each specialty details the eligibility criteria on its respective person specification. Generally for CT1/ST1 posts, you need to be on track to successfully complete your Foundation Programme competencies, or have an equivalent level of training from overseas.
There are experience caps for entry to ST1/CT1 posts. These range between 12 and 18 months depending on the Specialty. This is the maximum amount of experience you can have within that specialty (excluding medical school and Foundation School experience) in order to apply to the programme. Applicants with more than this level of experience will only be considered for CT2/ST2 posts or higher, depending on their level of experience. This is something to bear in mind if you are considering taking time out of training after the Foundation Programme.
Each year the Specialty Training website will also update the information regarding eligibility for Specialty, including details for internationally qualified doctors. Please have a look at this for further information regarding eligibility.