There is no way to guarantee that you'll get jobs. All you can do is bid on them and keep doing it. But, a few things can help.
1. Make sure to develop a good relationship with your client such that you can ask them or even guide them a bit as to how you'd like them to comment about the project with you. It's not that you are asking them to say something that's not true, but you can guide them to say what they might have been planning to say, but say it in a way that you think might be stronger. Other potential clients will then see that comment that might be more persuasive than a simple, "Would recommend this freelancer."
2. Keep your portfilio updated and add new work. Add the project you just finished and make sure to flesh it out so it looks really good and is fully explained. Do projects like the ones you want on your own and post the work. I have many personal works in my portfilio that I did for myself to show my range and skills. There is noting wrong with self-promotion.
3. Reference your successful job in your proposal. If a similar one is available, mention that you just finished one like it and it turned out really well. Mention what you learned or offer an expert tip to them to show them you are capable.
4. Never give up. It's not uncommon for me to bid on 30 projects before I land one. But sooner or later, you will and the track record starts to add up. It's hard to show success when you've only done one job but just keep bidding and keep bidding. Refne the way you bid and improve your technique and all of a sudden you'll get one or two at a time. If you are talented and you write good bids, you'll eventually start getting work. It took me a year to get my first project. Don't give up.
