<jats:title>Abstract</jats:title><jats:p>We discuss methods to determine <jats:italic>L</jats:italic>‐<jats:italic>M</jats:italic>‐<jats:italic>N</jats:italic> coordinate systems for current sheet crossings observed by the Magnetospheric Multiscale (MMS) spacecraft mission during ongoing reconnection, where <jats:bold>e</jats:bold><jats:sub><jats:italic>L</jats:italic></jats:sub> is the direction of the reconnecting component of the magnetic field, <jats:bold>B</jats:bold>, and <jats:bold>e</jats:bold><jats:sub><jats:italic>N</jats:italic></jats:sub> is normal to the magnetopause. We present and test a new hybrid method, with <jats:bold>e</jats:bold><jats:sub><jats:italic>L</jats:italic></jats:sub> estimated as the maximum variance direction of <jats:bold>B</jats:bold> (MVAB) and <jats:bold>e</jats:bold><jats:sub><jats:italic>N</jats:italic></jats:sub> as the direction of maximum directional derivative of <jats:bold>B</jats:bold>, and then adjust these directions to be perpendicular. In the best case, only small adjustment is needed. Results from this method, applied to an MMS crossing of the dayside magnetopause at 1305:45 UT on 16 October 2015, are discussed and compared with those from other methods for which <jats:bold>e</jats:bold><jats:sub><jats:italic>N</jats:italic></jats:sub> is obtained by other means. Each of the other evaluations can be combined with <jats:bold>e</jats:bold><jats:sub><jats:italic>L</jats:italic></jats:sub> from MVAB in a generalized hybrid approach to provide an <jats:italic>L</jats:italic>‐<jats:italic>M</jats:italic>‐<jats:italic>N</jats:italic> system. The quality of the results is judged by eigenvalue ratios, constancy of directions using different data segments and methods, and expected sign and magnitude of the normal component of <jats:bold>B</jats:bold>. For this event, the hybrid method appears to produce <jats:bold>e</jats:bold><jats:sub><jats:italic>N</jats:italic></jats:sub> accurate to within less than 10°. We discuss variance analysis using the electric current density, <jats:bold>J</jats:bold>, or the <jats:bold>J</jats:bold> × <jats:bold>B</jats:bold> force, which yield promising results, and minimum Faraday residue analysis and MVAB alone, which can be useful for other events. We also briefly discuss results from our hybrid method and MVAB alone for a few other MMS reconnection events.</jats:p>