Which column(s) to index in MySQL - mysql

Question

I'm trying to optimize the following table, according to phpMyAdmin several stats regarding Table Scans are high and indices do not exist or are not being used. (Handler read rnd next 5.7 M)
1.
$query = "
SELECT * FROM apps_discrep
WHERE discrep_station = '$station'
AND discrep_date = '$date'
ORDER BY discrep_timestart";
2.
$query = "
SELECT * FROM apps_discrep
WHERE discrep_date BETWEEN '$keyword' AND '$keyword3'
AND (discrep_station like '$keyword2%') ORDER BY discrep_date";
Would it be correct to Index discrep_station, discrep_date, and discrep_timestart?
There currently only exist the Primary Unique Index on the auto-increment ID.
-- Table structure
`index` int(11) NOT NULL AUTO_INCREMENT,
discrep_station varchar(5) NOT NULL,
discrep_timestart time NOT NULL,
discrep_timestop time NOT NULL,
discrep_date date NOT NULL,
discrep_datetime timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
discrep_show varchar(31) NOT NULL,
discrep_text text NOT NULL,
discrep_by varchar(11) NOT NULL,
discrep_opr varchar(11) NOT NULL,
email_traffic varchar(3) NOT NULL,
email_techs varchar(3) NOT NULL,
email_promos varchar(3) NOT NULL,
email_spots varchar(3) NOT NULL,
eas_row varchar(11) NOT NULL,
PRIMARY KEY (`index`)
ENGINE=MyISAM DEFAULT CHARSET=utf8;

Answer 1

It looks to me like you can get both queries with the same BTREE index, since that allows you to use the left-most tuples as a separate index.
Consider this MySQL doc page as a reference.
ALTER TABLE xxx ADD KEY `key1` (`discrep_station`, `discrep_date`, `discrep_timestart`) USING BTREE;
Your first query will use all 3 fields in the index. The second query will only use the first 2 fields in the index.