1) Yeah, as already said, for hitting two arrows at once, jump to them.
2) Keep both the arrows AND song in mind. This seems like a no-brainer, but you'd be surprised how many people only pay attention to one or the other. Once you know the flow of the song, knowing the flow of the arrows becomes a lot easier, since you know when certain patterns are likely to come up and the steps will go along with the beat. And, of course, most songs use the bass/backbeat to determine the flow of the steps. Sometimes its hard to hear in a melodic song where there are vocals and all kinds of other noise, but if you can pick up on the bass, in more cases than not, it will help you.
3) Also as said above, do not be afraid of leaving your foot on an arrow. The KEY thing beginners need to learn is to *flow* and that means NOT sitting in the center of the four arrows or returning to that position after every step. The game doesn't penalize you for having your foot on an arrow when there is empty space on the screen, it only penalizes you for *missing* an arrow. Learning to flow is how you learn to do the combinations, because you aren't wasting time returning to the center. Instead, you're moving your feet immediately to where they need to be. (i.e. > < v combo). Start off with your right foot on the right arrow, then hit the left arrow with your left foot, then slide your right foot from the right arrow to the down arrow and hit it. Once you get the pacing right, its that simple.
4) Reading the arrows. It seems impossible now to read the faster/more complex songs, but with practice, it will come to you. Even if the arrows don't physically slow down, they will looks slower to you with practice, because you'll be reading faster. Hell, after they added speed mods I would NEVER play without using 1.5x because that was comfortable for me.
5) I'm glad you decided to give the game a shot. A lot of people still have an unfair view of it. I can't blame them for hating the community that has sprung up around DDR. Most of them are emo/goth/angsty/punkass little bitches that cause nothing but drama. I was part of that community for a few years, but those of us who were there from the beginning were getting older and pissed off at the young posers trying to act like they were good. I could go on and on, but I won't. The game, despite the community, is still golden though. Its a lot of fun and it IS good exercise.
Anyway, if you have any more questions, post em.