Okay, firstly, the strength to winning matches is the ability to hold your serve. Usually, a set is won by holding every service game, then breaking your opponent serve. When this is the case wind the set 6-4.
If you serve the first game, you must to break at 5-4. If you serve the setting game you must break at 4-4.
Therefore, holding serve is the most important thing in a match. If you do loose your serve work VERY hard to break them straight back. You must put in 120% effort to break them immediately otherwise the whole match can change around in a few games.
Therefore your second serve is the anchor for the match. Potentially the second serve will be one of the major influences in the outcome of your matches. You need to work hard to develop a solid second serve you can rely on in ANY situation.
We often ignore serving practice. However we are guarenteed to need to hit that shot and hit it well !
Enjoy ! Michael