The optimization process and recommendations:

1. Avoid Selecting Unnecessary Columns (query line: 2): Avoid selecting all columns with the '*' wildcard, unless you intend to use them all. Selecting redundant columns may result in unnecessary performance degradation.

The optimized query:

SELECT
        * 
    FROM
        SO_SalesOrder so 
    INNER JOIN
        SO_Leg AS l 
            ON l.SalesOrder = so.SalesOrdernr 
    INNER JOIN
        SO_Cargo cg 
            ON cg.Cargonr = l.Cargo 
    INNER JOIN
        SO_Activity ea 
            ON ea.Activitynr = l.EndActivity 
    INNER JOIN
        SO_Activity ba 
            ON ba.Activitynr = l.BeginActivity 
    LEFT OUTER JOIN
        RP_TripActivity eta 
            ON eta.Activity = l.EndActivity 
    LEFT OUTER JOIN
        Product p 
            ON p.Productnr = cg.Product 
    WHERE
        ba.Date BETWEEN '2015-10-01 00:00:00' AND '2015-10-07 23:59:59' 
        AND OrderStatus != 2 
        AND so.Customer = 95