Im not a fan of Agents, but as its your first time I would use one. But check their fees - all their fees. They vary hugely for no apparent or good reason. If there is a choice chose an agent registered with ARLA or a large chain. It doesnt necessarily mean theyll be good, but you have a better chance and a chain of command to complain to.
When you go in to register with several have all your paperwork with you - neat and orgainsed. 3 months bank statements, ID, work details, references, 3 months payslips. They may not want to see it at this stage, but be prepared. Be smart and polite. Be upfront about any issues - debts, pets. Dont let an Agent tell you the landlord doesnt accept this or that, ask politely that they ask the landlord or perhaps offer to meet you (not saying theres anything negative about your situation!). I have chosen tenants that havent sounded ideal, but on meeting them have accepted them and been very glad that I did.
Once registered, phone regularly, as they will have forgotten about you!!
Dont rent a dump - if your told work will be done. Say youll go back when the work has been done. Chances are it will never be improved.
When you do find somewhere : check your contract carefully, check the inventory carefully, make sure your deposit will be protected (within 14 days you should have paperwwork from the Deposit scheme saying where it is).
Check smoke alarms and carbon monoxide alarms are provided and working.
Check there is a gas safety certificate, maybe a electrical safety certificate (not legal), instruction manuals, numbers to call for problems.
Finally, there are really strict laws for tenants and landlords. If theres something youre not happy about google, ask advice. Dont suffer in silence. You are needed by the Agent and the landlord, so dont be made to feel unimportant.
There are decent tenants and decent landlords with lovely properties - I just wish we meet up a bit more frequently!!
Wishing you the very best in the search for your new home.