You should ensure that you send intimation mail to admin department about the possible date of joining a candidate so that admin department can make necessary arrangement related to infra/equipment required by a candidate. Here timely intimation is very important. There could be chances that admin needs approval for a purchase of a new laptop, data card, mobile or anything else. If you will intimate them just a few days before candidate joining then they might not get time to arrange for such approval and procurement of required infra provided you should have enough time between offering candidate and his joining. Hence it is suggested to share intimation to admin department just after you send an offer letter to the candidate. Another good idea is to share intimation with them when a request is raised for additional manpower.
To ease the process, admin department should maintain a master list of infra requirement for each profile so that they can refer the list whenever they get intimation from HR department about candidate joining.
Another good idea, to ensure that everything is ready, you can seek confirmation from admin and IT department about readiness from their side.
Be in touch with candidate least twice before his date of joining. I would suggest 15 days before and one day before his date of joining. During that conversation, you can also remind him about various documents which he needs to take along with him on DOJ.