As Manator has said most of it is common sense,however it is also individual to the working environment,tripping over a trailing cable on the ground will potentially have a far different outcome to tripping over one say 30 feet up on a scaffold.
Risk assessments just need a little thought and the person doing them needs to be familiar with that particular process or piece of equipment.that is why they are usually carried out by someone higher up the chain.Let us take an angle grinder for example,now the ordinary person may see the risks as eye injury from flying sparks,they may even think about the risk of fire from those sparks coming into contact with flammable material.How many would think of the possibility of a disc shattering or becoming detached from the machine?
Most of us do risk assessments every day without thinking about them,it's only when someone puts you on the spot that you start to panic.
Look at this for one we do every day.
Wake up and get dressed,what are the risks? Well standing up and trying to put trousers on,you could fall and bang your head,you limit this risk by sitting on the bed and putting your trousers on.
Make breakfast, put kettle on to boil,the risk here is possible electric shock and scalding.So you make sure your hands are dry before plugging in kettle and you don't overfill it so it won't splash boiling water.Having made the tea you wait for it to cool slightly before drinking it,if the milk has been in the fridge for a few days you'll sniff or taste it before putting it on your cornflakes,if it's off you risk food poisoning.
Driving to work.Check car windows are clear,if they're covered in frost the risk is you'll hit something because you can't see,so you clear the windows to reduce the risk!
Easy isn't it? it's like anything the first time you do one you will find it hard and you'll probably miss things out,it comes with time and experience.The most important thing to remember is if ever you are uncomfortable doing a RA then say so,if someone asks you and you're not familiar with that particular process or piece of equipment then speak out.It's far better to say "I'm sorry I don't have enough experience with this to do an accurate RA" than to miss something out and someone gets hurt as a result.Quite often a RA will be done by more than one person,partly by you and partly by another person,lifting a heavy motor or transformer for example,the crane operator will be more familiar with the risks during the lift and you'll be more familiar with the electrical side of it,therefore you do the RA together.