1. Offer unique value
Go beyond the limits of a job board. Offer more than just a way to publish jobs. See what companies really need. Install also a blog and provide good information related to your target users.
2. The right domain
Before installing your application, do a complete analysis of your competitors and for specific keywords. Then, choose the right domain name.
3. Create more value than you capture
Focus on quality, but have a clear thought about monetization.
4. Good SEO
5. Brand yourself
Learn to communicate your unique value in one sentence.