yes, it is hard to get in depending on your category.
follow the rules for submission and do not over submit. Wait 6 months or so to re-submit in case you're not in.
Also visit
SEO forums where a lot of DMOZ editors hangout and some may give you input on expected inclusion time.
I also would not hold my breath on DMOZ....do other relevant link building....getting in DMOZ will not shoot up in the rankings.
You can learn more about
SEO from my site www.montegroup.com where you'll find links to my blog.