Ask questions which show you have interest in the company and enthusiasm for the job. And remember, don't let rejections get you down. They often have nothing to do with you personally. Many experts say it's a number's game, so every rejection gets you closer to an offer. There are many published sources for this kind of information.
Web sites are another source of salary data, but be careful, they are voluminous.
Be informed about how to negotiate as well as what can and cannot be negotiated. Some employers have a range of flexibility when it comes to salary, others have flexibility with benefits, still others will have a take it or leave it approach. But most importantly, never attempt to negotiate until an offer has been made. Furthermore, there are benefits that some employers may not offer up front but which might be crucial to your decision. Some examples are relocation assistance, payment for membership in professional organizations, training opportunities, or parking and commuting discounts.