I sometimes get asked to help my friends and family when they have to write things. In the last few months, I've offered more or less the same advice to a lady writing a eulogy and a gent stuck with a best man's speech. That advice seemed to work out okay, so here's what I said...
You've been chosen to write this because you know the person well.
Maybe you've not known them as long as other people who'll be there. That doesn't matter. You know them and I don't. If I asked you, "What are they like?", you could tell me.
And you probably wouldn't start by telling me how tall or old or fat they are, but the kind of person they are. To do that, you can probably think of something they once did that tells me exactly what they're like. You can probably think of three different things they once did that gives me a rounded picture.
A time that shows their sense of humour. A time that shows what they were especially good or bad at. A time they were kind or brave.
At least one of those stories should involve you. Another story might be one you've been told by someone else about the person. Something that when you heard it made you think, “Yes, that's exactly them”.
(When someone dies, their friends and family tend to tell stories about things they've done. Ask around.)
Write these stories down. Write them as if you're telling them to me over tea and biscuits. Keep things informal and simple.
Some people like to write the whole speech out in full. Some people just want bullet-points on note cards, so they can make it up as they go. If you're not sure which works best for you, write it out in full and then see how easy you find to read it out loud. You can always have notes on the day.
Put the best story last.
Then think about how you're going to start. It might be something as simple as: “What sort of person is X? Here are three examples...”. Or explain, briefly, how you knew the person and why (you think) you've been been chosen to speak.
If you're going to do jokes, put a first joke in early so people know what to expect.
Go over what you've written. Cut it down. Keep it short and to the point.
Read it out loud to yourself. It feels a bit weird but it really helps. Make sure you can read it without running out of breath or stumbling over the words. Time how long it takes - but make sure you're reading at the same speed you'll read it on the day. Don't rush.
Read your speech to someone you trust and who knows the person – and won't go telling people what you're about to say. Listen to what they say afterwards. More importantly, watch how they react while you're speaking. Rewrite the bits that need it.
Don't drink before you deliver it. Make sure someone else has a copy of the speech in case you lose yours.
Speak up, so people at the back can hear you. Don't rush.
Remember that the audience is on your side: they want you to do well.