Wedding speeches are not nerve racking as some people think.To give a memorable speech.you first have to rase every negative thoughts about speaking in public.See yourself as someone who have the gut to speak in public.When you do so,confidence kicks in and your body,soul and spirit is positively energised.And so, fear is held at bay.
You should also decide on the style of delivery.Though humorous wedding speeches will make everyone falll in love with you,you should stay off it if you are not the funny type.Give the speech in your own style and you will be celebrated for that.Usually emotional,narrative,humor or a blendof two or more styles is what you can opt for.
Brainstorm for sometime about the couple and do write fascinating things about them-where they met,how they are well suited,their individual accomplishments ...can spark warm memories.
Dedicate sometime and day to write so that you dont just scribbble anything when you realise later that you have to make a speech.
You should write using words which are easy to understand and avoid commenting on issues like ex-boy/girlfriends,religion(UNLESS YOU ARE PRETTY SURE THAT MOST GUESTS HAVE A STRONG RELIGIOUS HERITAGE OR BACKGROUND)
Let someone look over your speech and trim off words which are not suitable for the word.
Once your speech is ready,do practise and envision what you want to say.