Some of the points here have been raised above, but repetition isn’t always a bad thing, What UKNS has said above, I haven't mentioned, but if you want to be a serious batsman in league cricket, try to get youself batting in tthe top 3...
Firstly, before you go out to bat, work out how long it will take you on an average day to score 100 runs – for me my average run rate is about 90 runs per 100 balls (90/100 = 0.9). On this basis I will need to face about 111 balls to score a ton in league cricket (100/0.9). In overs terms assuming an equal strike rate (which never happens but park that for the moment) you then have 111/6 =18.5, 18.5 x 2 = 37 overs.
Given the maths above, mentally I need to be able to bat for at least 35-40 overs to score 100. Knowing that is the first step. To bat for 40 overs you are looking at being at the crease for 2½ hours, typically. Obviously in Sunday cricket, or lower standards you can accelerate the times and runs per ball, but the message is, are you prepared to bat for 2½ hours? If not, you either need to get a shift on and take more risks or rely on it being your lucky day.
Mentally if you are ready and you mind is clear enough you have already taken the first steps.
Next, before you go out to bat make sure all your equipment is comfortable, if you aren’t comfortable you will lose concentration early in your innings, which is bad news.
Then you are walking out to bat – the first 5 overs are the hardest for a batsman, (ignore the state of the game for a moment) You need to play yourself in, only play low risk shots accepting that it is always nice to get an early boundary to give you confidence. If you do get a rank bad ball early on, commit 100% to smacking it, don’t have a waft. Running well between the wickets also helps get the blood flowing and your feet moving when it is you are on strike. Really look to rotate the strike so the fielding side are pushed onto the back foot (sorry for the clichés, but they work).
Also be aware of where the fielders are standing or where they have been moved to, if the bowler is bowing to a 7-2 offside field, it is likely he is trying to move the ball away from you on a full length – so sitting on you back foot looking to work the ball through the leg side won’t be a low risk shot and also be weary of the outside off stump waft... i try to encourage players, especially early on to “keep your shape” stay playing shots under your eyes early on and keep it really simple.
After about 5 or 6 overs, you should be into your innings – possibly on 10 to 15 or maybe you have got a bit of a flyer and are on 25 plus. At this point be warned it is easy to feel "in" when you aren't quite there yet and remember most time a batsman is out he has given it away playing a bat shot, rather than being got out by the bowler (thus spoke a batsman!!)
By this time you are in for the long hall – break your knock down into 5 over bursts, pick up the boundaries and play your own way. Don’t panic if the ball is doing a bit, keep calm and wait for the bad balls, at most levels of cricket there are two four balls every two overs.
The important think by this stage is that you are in your own “bubble”, I don’t think too much about what is being said to me, either “instructions” from the wicket keeper or “advice” from the slips, I just try to keep my mind clear and think about respecting the bowler and watching the ball.
After about 15 overs you team mate are giving you a polite ripple and you wave back, while there is always one shouting “Double it up fella”. You are mentally all ready for that. Don’t think about your own runs, the easiest think is look at the total and work on getting your team into a good position at this point. It will take your mind off your own innings and Cricket is a team game after all...
At some stage you are likely to lose your concentration, for some it is around 35, for others around 60, or it can happen around a break in play, such as a drinks break, but it does happen. To try to stop that, you need to stay in your bubble – think Jonathan Trott still marking out his guard after he has won the match!! I think the example of Jonny Wilkinson taking a penalty or conversion is a better example usually. Don’t be afraid to take a couple of overs to “play yourself in” again if you feel like your concentration is going, it will come back pretty quick.
Usually you will need some luck, sometime you wont, but if you get some, double your efforts not to give it away.
Not giving it away is a massive deal by this stage in you knock, after 25-30 overs you are heading towards the “zone” you are on about 80 and right on top. At this point, trying to farm the strike is my usually tactic – slightly selfish I know, but unless the other batter is smashing the ball everywhere, you are the in form player and will score runs the fastest so it is a legitimate thing to do.
As a rough rule of thumb if there are no scoreboards on the ground sometimes it is good to know what you are on – look at the total guess what proportion of runs you have and take 10-15 from that usually gets you pretty close.
Either way – you are heading towards the 90’s. Try not to change how you have been playing but for the last 10 runs, bat them as if they are your first 10, go back to “keeping your shape” running the singles hard and committing 100% to going for the shot.
Then the big moment arrives. Well done. But DONT GIVE IT AWAY!
Once you get to about 110 you are suddenly in the zone – where every ball can be deposited anywhere at will, in fact you will feel like the bowlers are actually bowling where you want them to – when you get to this point if you give it away, you have let your team down. Concentrate doubly hard and as Goochie says “Make it a BIGGY”
Obviously there are loads of other factors – the different bowlers, the different match situations, the different types of match, a decent oppo skipper who can try and get you off strike... but the principles are there.