The optimization process and recommendations:

1. Avoid Selecting Unnecessary Columns (query line: 11): Avoid selecting all columns with the '*' wildcard, unless you intend to use them all. Selecting redundant columns may result in unnecessary performance degradation.
2. Avoid Subqueries (query line: 10): We advise against using subqueries as they are not optimized well by the optimizer. Therefore, it's recommended to join a newly created temporary table that holds the data, which also includes the relevant search index.
3. Create Optimal Indexes (modified query below): The recommended indexes are an integral part of this optimization effort and should be created before testing the execution duration of the optimized query.
4. Prefer Direct Join Over Joined Subquery (query line: 14): We advise against using subqueries as they are not optimized well by the optimizer. Therefore, we recommend to replace subqueries with JOIN clauses.

Optimal indexes for this query:

ALTER TABLE `User_Info` ADD INDEX `user_info_idx_action_user_name_url` (`action`,`user_name`,`url`);

The optimized query:

SELECT
        * 
    FROM
        (SELECT
            info.*,
            ROW_NUMBER() OVER (ORDER 
        BY
            info.modified_date DESC) rn 
        FROM
            (SELECT
                info.*,
                Count(*) OVER () AS info_count 
            FROM
                User_Info info 
            WHERE
                (
                    (
                        info.url LIKE 'url://%'
                    ) 
                    AND (
                        info.action = 'Action1'
                    ) 
                    AND info.user_name = 'john' 
                    AND info.modified_date >= '04/01/2014 00:00:00' 
                    AND info.modified_date <= '04/12/2014 23:59:59'
                )) info) info 
        WHERE
            rn >= 1 
            AND rn <= 100