Troubleshooting of the blocking and concurrency issues is, in the nutshells, a simple process. You need to identify the processes involved in blocking conditions or deadlocks and analyze why those processes acquire the locks on the same resources. In majority of cases, you need to analyze queries and their execution plans identifying possible inefficiencies that led to excessive number of locks being acquired.
Collecting this information is not a trivial task. The information is exposed through DMVs (you can download the set of scripts here); however, it requires you to run the queries at time when blocking occurred. Fortunately, SQL Server allows you to capture blocking and deadlock conditions with the blocked process report and deadlock graph, analyzing them later.
There is the caveat though. Neither blocked process report nor deadlock graph provide you execution plans of the statements. Nor do they always include affected statements in the plain text. You may need to query plan cache and other DMVs to get this information and longer you wait lesser is the chance that the information is available. Moreover, SQL Server may generate enormous number of blocked process reports in cases of prolonged blocking and complex blocking chains, which complicates the analysis.
Confirmed to work with SQL Server 2012 and later, but might work on earlier versions as well. Dmitri has released it to the public, so check it out.