Well I play baseball in college currently, and I play MLB just like I really hit. I will usually take the first pitch. I look to avoid any breaking balls that are low, chances are that it's either going to be a ball or you will not make solid contact. I'm very patient and wait for my pitch, unless it's 0-2 I will try to avoid all breaking balls unless it's up in the zone, and I wait for a fastball/changeup to be thrown.
As far as determining what the pitch is? Heres some tips
1.) Sliders are easy to tell but sometimes it's easy to mix it up with a cutter. Lets say you got a right handed hitter up and your facing a RHP. You know his slider and cutter will break away from you. Those will be the only pitches that have a lot of lateral movement away from your bat. Unless the pitcher has both a slider and a cutter, you can see that pretty well. Do not swing at a slider low in the zone or away, if its breaking in high or they try to back door it and put it on the inside it loses some movement and flattens out.
2.) Curves are also easy to tell somewhat. There are 2 different kinds, a 12-6 curve, and a standard curve. A normal curve is just like a slider but it will have less lateral movement, more vertical movement, and will usually be slower. The harder curve to hit is the 12-6. If you see a pitch that is coming relatively slow, and has a lot of break, it's a 12-6 curve. 12-6 curve's are slow enough to see that it's coming in with a lot of break, thus, you being able to see it's a 12-6 curve. When the pitch is getting close to you is when you decide if it's a ball or strike. If you see it coming in high in the zone, then usually it will end up as a strike on the bottom or just below the K zone. If you see the curve is coming in down the middle avoid it at all costs. Only swing at a 12-6 if it's gonna be a close call and it's an 0-2 count, or you see it's gonna break into the top half of the zone. Any breaking ball in the top half of the zone will always flatten out and makes for an easy drive.
3.) Fastballs. A splitter is a mix between a fastball and a 12-6 curve somewhat. They are generally pretty fast and are classified as a fast ball. They have good vertical break late. If the pitcher has a splitter and you see a fastball coming in low, you will have to use your best judgement to if the ball is breaking and is a splitter, or just a low fastball. Sinkers don't really break. They are thrown on a rail. What that means is they leave the pitchers hand going in basically a straight diagonal line breaking down into the plate. Hitters will generally swing over the top of it because the angle it's coming in at, thus making a good ground ball pitch. The best way to nail a sinker is to get under it. If it's coming in low, getting under it could be really tough. But if that thing gets left in the top half, it's nothing more than a slow non moving fastball. Cutters and 2 seamer's are easy to tell. They will be the coming in at pretty good speed but you can tell by if it has slight break to the right or left. Cutters go from right-to-left when a RHP is throwing, and 2 seamer's go from left-to-right when a RHP is throwing.
Hope this somewhat helps.