Me and my brother have been shooting pigs in the uk for about six to Severn years.
The following is some of the things we have found.
Generally if you have pigs visiting ground fairly regularly they will normally respond to being fed quite easily.Chopped or whole maize seem to be favorite but i know boys who have had success with barley.make sure you bury feed or you will feed all the local badgers,deer and birds.
If your feeding close to a wood that doesn't belong to you you can draw them to where you want by moving the place you feed them about 50 yards every couple of days to where you finally want to shoot them. I prefer to get them 150 to 200 yards from the wood to allow for runners.A word of warning it doesn't take many pigs to make a lot of mess.Check with the land owner before you start feeding.
High seats are not necessary but advisable i have shot them sat under hedges,sat in barns or just sat on a bank over looking baiting points.
Pigs might not see you but they will wind you ,once they do you will hear a loud grunt and see there little piggy arses disappearing into the distance.
Once you get them feeding don't shoot them to soon, let them get confidence they will be easier to shoot when there feeding confidently they seem to be very greedy and almost oblivious to there surroundings when there is large group of pigs feeding with confidence.
As for calibres we have shot them with .270 .308 and 300wsm
if i was buying a rifle to be used mainly on pigs i would opt for .30 cal.I have had no problems with the .270 and the biggest pigs we shot have been with .270 but i always seem a little more comfortable with the .300 in my grubby little mitts.
Try not to shoot big sows shoot the piglets of her normally she will bring them back to the feed at least a few times therefore allowing you to shoot a couple.
Finally before you shoot a monster think how you are going to retrieve it big pigs are pain in the arse to move i learnt this the hard way
I must say that i do not proclaim to be an expert not by a long chalk .I hope what i have wrote is some use or of interest to someone despite my spelling mistakes and bad grammar.Perhaps Mr davies would like to add something to what Ive wrote rumour has it he's managed to scrape the odd one down now and then
ATB SEAN