As an experienced therapist with high standards, we expect you'll make a client feel comfortable and heard, and that you will be honest with them about what they can expect from therapy and if you have the right skill set to help them.
Otherwise, we'd ask that you discuss with the client their motivation to continue sessions, ideally looking for a minimum commitment of three to four sessions which would allow you time to complete an extended assessment. This does depend on how you work however, so if you usually work within a certain number of sessions or 'blocks' of sessions (or if you work on an open-ended basis), we would recommend discussing this so your client is aware of how you tend to work, and what they can expect in agreeing to continue working with you.
If you have any expectations of your clients, we would also recommend discussing these in the initial session (and potentially in your profile Bio so clients know what to expect prior to booking) - for example, if your approach usually includes homework, it would be beneficial for clients to be aware of this expectation so they can decide if this type of therapy is right for them and what they are seeking.
We would also ask that you discuss topics such as the 48-hour cancellation policy, rearrangements, how to contact you, what they should do if they want to pause or stop sessions, and the terms and conditions (T&C's). Even though all clients agree to the T&Cs (including the 48-hour cancellation policy) when booking their initial session, in our experience clients tend to absorb more when these details are reiterated in the first session to ensure they have a full understanding. This also gives the clients time to ask any questions they have regarding practicalities etc.
Lastly, we would recommend you review any guidance from your professional body regarding initial sessions and new clients, and keep up to date on any new guidance they share with registrants.