All you need to do know is to put yourself in front of a word processor or a piece of paper and then write. You can try and do this for a particular amount of time or you can keep working until you feel you are done. What is important, here, however, is that you continue without pausing or editing.
It does not matter, at this stage, if you make any mistakes or if anything does just not sound as good as you think it should. Once you are finished, your next step is to look over what you have written and make a note of anything that stands out to you. You can then go on to use these to prompt poems or to arrange them into one poem if that is what you want to do.
This exercise has helped you capture something important about your own feelings. This, in the end, will help you produce better content than trying to craft something that sounds like you think good poetry ought to be. This will help you put across what you want to say, as well as elicit an emotional response from your readers.
If you are more genuine in your words, they will be more genuine in their emotion. There are more things to know, however, when it comes to helping your work look less trite. If you want to sound original and fresh, you should, of course, avoid known cliches. This means things that you have heard too many times because the same will have gone for your reader.
From your notes, consider what similes and metaphors you could come up with. This can take a lot more time, but, if you write regularly, you will become better at putting together an effective image. One exercise you could do is to take on individual cliches by taking what they say and making something new.
You should also keep in mind that, while emotion is good, you should make sure to avoid sentimentality. You want your emotion to be genuine. Do not force it into your poems and the audience will have a more personal reaction to them. Another thing to remember is to not use too many abstract words. These detract from the impact of your poem as tangible imagery will elicit more for readers.
Your readers should not be told outright that you are angry, sad or happy, they should, instead, be given concrete imagery to understand those feelings. Do not, as you write, consider editing too much, though. You need to just get your poem on the page, to start with, before you can do that. Start revising what you have written after that, and it is a very important stage that should not be skipped. You will, eventually, have the first of your joyful poems.