Being able to communicate on the radio is an important skill to learn to get comfortable with. The more confident you are, the less distracting radio is to your ability to focus on flying and navigating.
Sticking to a standard "script" helps to keep things concise and accurate, meaning less chance for misunderstandings. If you know more or less what the "script" is, it becomes fairly second-nature and much easier when you are under pressure
This is the CAA "bible" for communications. It's a lengthy but well presented document which covers a whole range of scenarios. Don't try to read in one sitting - think of this as a reference document to be dipped into frequently
This leaflet is targeted specifically at VFR pilots, so ideal for students. It is shorter and more easily digested than CAP413, so do try to read through at least once from start to end as you get to grips with RT. It has practical advice on use of equipment in the aircraft
The Practical Test - in order to be issues with a radio licence (FRTOL), you must pass a practical RT test. This is a separate thing from the written Communications exam. Your school will advise you on how to prepare for and apply to take the test. Read CAP2325 carefully - this provides guidance what the test involves
You can take the flying skills test before the practical RT test, but I recommend if possible doing it beforehand, so that as soon as you pass your skills test you can submit your licence application and look forward to the freedom of flying without supervision
Tips to help become confident with RT
Always have pen in hand before you press the button so you can jot down notes and complete your readback confidently. If a controller gives you more information than you expected, you'll have forgotten the first bit before you realize you should have noted it down, and by then it's too late to get the pen out
Use a shorthand for making notes. For example if the controller said "Taxi across the grass, across runway 18, via taxiway Alpha hold Alpha 1", just jot down "G R18 A A1" which should be enough to make your readback easy and complete
Try to understand the purpose of each communication and how it is relevant to the person you are talking to. If you understand what they need to hear from you it will be much easier to remember what to say
Before you begin any communication, think about what you expect to hear. It might not be right, but most times it will be close. It's much easier to understand what someone is saying to you if you anticipate what they are going to say. But do listen carefully to avoid confirmation bias (i.e. "hearing" what you expect even if that's not what was said!)
If you get in a twist, you can always buy time by simply saying "Stand by". Sort yourself out, be calm, and when ready to resume communication, start over or resume where you left off
If you didn't hear or didn't understand what was said, just say "Say again". If you do this more than once, the controller will likely say it again in a simpler way or more slowly, as they will know you are struggling to understand
Although you can use written templates or cribs to help you to remember how to make standard calls, you'll never learn to remember the calls if you rely on these too long. They also clutter up the cockpit and can become a distraction. So ditch these after the first couple of tries, and you will quickly get the hang of it without them
Practice standard RT sequences driving your car, in the shower, walking the dog....you get the idea
If you are still struggling with radio calls beyond a reasonable point in your course (you'll know when that is), there are some additional things you could do to help:
Ask to visit the tower if there's one at your airfield, and sit and listen to the controller side for an hour or two
Get hold of an air-band radio, and park up near an a busy GA airfield and listen in. Your flying school might have a radio so you can do it there
Ask your flying school to recommend an instructor who can provide ground-based training and practice
There are quite a few YouTube videos offering advice and help, but make sure you use ones based on UK practices - the US is quite different
Remember the controller is just another human there to assist you, they are not trying to catch you out!