Rankings are pretty much worthless these days due to personalization and localization. Google shows different results depending on your previous searches (search history). They also change depending on which results you clicked on previously and likely whether or not you bounced once you clicked through.
Additionally, rankings in New York are totally different than those in Miami which are different than those in Houston which are different than those in Los Angeles. Results vary even more widely between countries.
If you’re looking for fairly reliable rankings in the US, for example, you would need to pull rankings for the same keyword in 25-50 major cities around the country (using proxy IPs that resolve to each of those cities) and then average them. Also need to clear search history, cookies, etc. after each individual pull.
If you want to do a spot check to see if a site comes up on the first page or two of Google, we will turn on a VPN which anonymizes my IP address and changes my location to something semi-random. We use private browsing too. It’s interesting to see how different the search results are when this is done.
Remember that search engine results are now highly contextual to the searcher’s environment, GEO, device, history etc. With so many variables unique to the individual searcher you will never be able to replicate the same context and develop a reliable ranking report by which to track progress. You can make some generalities; however these results will often be misleading and could result in your pursuit of false goals.
The best way to influence search results is to build a massive Google+ network because it really pays off. When people in your network (which include your 2nd and 3rd degree connections) perform a search for a product or service that you’re relevant for, all things being equal, you will appear higher to that searcher than sites that are not in any way linked to the searcher. This is particularly relevant to local search.
Below is the list of few tools which you can use for keyword ranking