Looking for Tips and Advice on Eulogies

There have been a few times recently when a close friend or family member have passed away and I have been asked to give a eulogy. I have never felt like I was able to because it seems so intimidating and I would not even know where to begin. I have been looking for tips and advice on eulogies. I have a few family members that have been very sick lately and as much as I do not like to think about it, I know that there will be a time when it will be necessary to speak at their funerals. I would like to be prepared and give them a proper eulogy.