Tips for using DML Statements
As @Nick suggested, this question is too broad to have straight forward answer. Are you looking for how to write queries ?? Or you are looking for commonly used best practices for any query ?? Or something else ??
May be for starter you can google around this question, or look at some of the following sites,

http://blog.sqlauthority.com/2009/01/20/sql-server-rules-for-optimizining-any-query-best-practices-for-query-optimization/

http://www.databasejournal.com/features/mssql/article.php/3827091/T-SQL-Best-Practices.htm

http://www.sql-server-performance.com/2001/sql-best-practices/

http://www.codeproject.com/Articles/34372/Top-10-steps-to-optimize-data-access-in-SQL-Server