I have to give my first demonstration speech siguiente week and I plan to speak on how to housetrain a dog. Any consejos on visual aids o on speaking in general? This is totally new to me. Thanks so much!

Firstly if tu know your subject and its something that interests tu thats half the battle won. As tu probably know the information so well tu will be able to talk about it without notes well just with a few pointers rather than full written notes. Secondly deep breathing try not to panic. Thirdly I am sure your audiance will understand if tu are not perfect. Finally pick a spot at the back of the room and if tu feel your nerves are getting the better of tu keep going but concentrate on the spot until tu get your confidence back. Hope this helps and good luck. I have done talks on my Thimble Collection in the past and that I did find scary so I know what tu are feeling.

Ok, when presenting a speech, dont stand in one spot, make sure u mover around a lil. Make sure tu project, look at your audience, and dont have your Q cards as a saftey shield. Make sure tu add character in your voice and face, and just make sure tu read it properly. Some people add to much emphasis at the wrong time which looks dogdey. EG:
And carbon emmisions went UP *2 segundo pause* 33 percent. :D see, that failed. Dont do that >.< and dont be nervous. There will be about 30 speeches that day, tu wont be remembered por your collegues. Unleass tu SCREWWW IT UUUP D:< o if its rly good and ppl amor IT ^-^

I've never had a problem with public speaking before, i'm nervous at the beginning but as soon as i start to roll i'm fine about.

What tu could do, is before tu give your speech is breathe. Inhale, hold for three segundos and exhale longer then tu inhaled. This will slow your corazón rate, stop the adrenilin pumping through your system and calm tu down.
Make sure you're voice is clear and loud but not deafening. What tu could do, to get the right volume, is ask a friend to sit/stand at the back of the hall a few days before the speech for a fraction of your speech and experiment with volumes. tu don't want to be talking normally as no one will hear you, but tu also don't want to scream out the words. Find what's best for you.
Walk around a little, but always keep your face and voice pointed to your audience, o at least to the side if mostrando them something.
Emphasise with your hands. If something is particularly important, hammer it in por connecting your hands together etc.
Visual aids - do tu mean to help tu remember what you're talking about o to mostrar them what tu mean?
To help tu remember tu could write on your hand the beginning of a sentance, o code words for certain subjects. Print out a sheet of paper with different little pictures for each subject tu want to cover and just carry around with you/place it on a mesa, tabla so if tu get stuck tu can calmly walk up to it (don't forget to continue talking) and sneak a peek before tu begin your siguiente subject.
To help them understand what tu mean, have tu thought of a slide-show? o even better, getting a friend to help and actually bring a house-trained dog to mostrar what tu mean.