What advice would you give to a person who is playing Trombone for the first time?

private lessons, definitely

Don't drop the slide!

Also, don't use oil or cream on the slide. Use Slide-O-Mix. That seems to be the way to go. I switched to Slide-O-Mix a couple years ago, and haven't looked back. Less buildup on the slide, and quicker and smoother action.

As far as practicing, do lots of long tones and focus on getting the most beautiful sound you can. Use a tuner to make sure that your slide positions are correct and to see if you're playing in tune.

have you played any other instrument? do you know how to read music? how well/long are you going to be intersted in the horn, do you want to get really good at it or just be able to say i know the basics of the trombone? do you already know how to play the instrument (how to form your mouth to play the notes) all of this all points towards one thing...private lessons and getting active in a band of some sort (community band for example). but yah, private lessons deffently.

"Also, don't use oil or cream on the slide. Use Slide-O-Mix. That seems to be the way to go. I switched to Slide-O-Mix a couple years ago, and haven't looked back. Less buildup on the slide, and quicker and smoother action."

I used to feel the same way, until the Slide Dr converted me back to superslick after setting up one of my slides.. the big caveat is, most people use way too much of the stuff!!!! this link has his system for cleaning and properly using creams (and slide-o-mix, for that matter)
http://www.slidedr.com/sickslide.htm
now that i use it properly, superslick cream has served me very well.. but it all comes down to preference, I guess.

You took the words right out of my mouth. I used Pledge for some time, and tried Slideomix, but for the last 10 or so years I have been exclusively using SuperSlick. I have found nothing that works better, all you have to do is use it correctly.

I don't see too many people using creams any more, and my repair tech said that the creams are becoming a thing of the past. However, some trombonists still like their Superslick and Trombotine, and if they're happy with it, that's fine with me.

The first time that I tried to covert to SOM, it didn't work too well for me. My slide kept drying out after every twenty minutes of playing, while the cream would last for two or three days, depending on how much playing I did over that time. So I gave up on the SOM and went back to the cream. A couple years later I tried the SOM again, after becoming frustrated with how gunked up my slide got. I stuck with it thist time, and it took about six months of constant use on the slide before it started working really well. Seems like it needed a "break-in" period.

^I have noticed that about slide o mix too. I was a superslick player for a long time, until recently when I moved and everyone in my section used SOM. I've used it and it seems like it does dry out rather fast, but I found it does work great, and I only used the first bottle. I'm going to get some of my own, and try proper usage of both to side by side them.