Trulia thank you for asking that question. If by up and coming neighborhood you mean activity then local schools, businesses, shopping and housing markets on the increase would be a good indicator of an up and coming neighborhood. Checking with the city planning and city reports to see what businesses are looking to move into the area. What area's are slated for new development with restaurants, shopping and activities are another indicator.
When searching it's always best to look for what's important to you. What one person believes is a good indicator someone else may deem as not.
Have a great weekend and when thinking real estate in the Phoenix market, keep me in mind.
Real Estate Professional Keller Williams Sonoran Living