For the adwords promo code, you can find it anywhere on the net. There is 100$, 75$, 50$ and some others deals. Mostly work only in US but there is some from any country I think. I live in Canada and I got mine by mail a year after signing up to adwords. Be careful when signing up, if you use the promo found online, it only work on new adwords account. So follow the step by step carefully to be sure to get the free credit. When I first signed up to adwords, I used a promo that was running on youtube. It was 75$ credit I think. I blow it up in less than 2 days on useless pay per impressions, that mean I was paying for my ads to be "view" even if they was no click on it. (ex: 20,000 impressions = 10$). I don't think this even exist anymore... So when I got my 100$ promo code, I used it wisely this time.
The only tricks I can give you is these one. Create a video campaigns for the video you want to promote
1- Set your bid to a maximum of 0.01$/click
2- On the
placement tab: add youtube.com. That way, in my understanding, your ads will only be seen on youtube.com. So in theory, every clicks will give you a views on your video and a chance to get new subscriber, because the people seeing it are people using youtube already.
3- Add keywords on the
youtube search keywords tab. Use popular keywords that will reach the audience you want, not necessarily keywords related to what your video is about. (Ex: I used the keyword "cats" for a video a made with a baby vlogging. Why? Because, my baby video is more popular with girls and women. And in my thought, people looking for cats videos are more likely being young girls and bored women...
4- Set your maximum budget to 1 or 2$ a day. Then when you reach your max budget, 1 or 2 hours after, check your video stats to see if your views increased. If not, change your setting. If yes, you can increase your daily budget to get more views for that day.
So with all these setting, you should get real views that will cost 0.01$/view. (my % is about 95%) Only drawback to these setting is that the minimum 0.01$ bid may not always get you many "impressions" in a day, so you'll get more views but slowly.
Oh... and if you are promoting a video that is already monetized by you, you may get back around 10 to 20% of your cost in your adsense account (if you are lucky) because people reaching your video through your ads are most likely be willing to click or watch an ads on your video.
I hope this will help...