First and foremost, sort your CV out; being at University you have access to free career advice! Get in-touch with your careers service (Career Hub at the University of Liverpool) and they will help you build and mould your CV to suit the positions you will be applying for. Once you have your CV organised, use your printing credit to print at least 50 copies of your CV.
I would recommend looking for a job on a weekday; the less busy a place is, the less likely your CV will be misplaced. Also, leave early in the morning as there are tons of places to apply and therefore a lot of walking to do. As there is a lot of walking it is a good idea to wear comfy shoes. As for the rest of your outfit, you can dress casual when giving your CV out, just make sure you look clean and your clothes are actually clean!
Another tip is to be enthusiastic; yeah the first couple of places you hand your CV to might be nerve-wracking, especially for us ‘less-social’ people, however, I assure you after about five applications you will be used to it.
Finally, there may be a lot of places which require an online application e.g. Debenhams; if you are not sure whether a shop/restaurant requires this, offer your CV anyway and they will let you know what to do.
Looking for a job in Liverpool is really easy as you have access to thousands of retail and food places to apply. You will probably not hear back from all of the places you give your CV to, however you are guaranteed to be contacted by at least one due to the abundance of shops you can approach.