How should I start "heavy lifting?"

Watch videos on form or ask a trainer.

I'd like to start heavy lifting to see how it improves my physique. I'm guessing heavy lifting isn't just using the machines at the gym that guide your motions? Do you have any tips for a beginner?

As someone who has injured themself a number of times, start with a moderate-light weight, and practice getting your form down first. Check out some books or videos. See how the exercises are supposed to look, and check yoursefl out in the mirror. Once you have the form down, start adding the weight gradually until you are challenged properly.

I have trouble with this. I always want to jump in full bore, and end up with a messed up shoulder or elbow, or something.

As a number of the people here have pointed to there are a ton of books, videos, magazines, sources of information out there.

If you have never lifted before a Trainer might be a good place to start. You may only need 4 or 5 sessions to help get you started. (They might try to sell you more, but if you are self diciplined you only need to basics.) But they can probably teach you muscles, groups, routines, exercises that work best for you, should you work legs once a week or twice, etc.... A Good Trainer can give you a good foundation. Everyone is a little different and you will find things that you like and things that you do not. The key is as you are getting started, start light, and worry more about the form. Bad form leads to poor results, and worse, injury.

If you like it, after a few months if you are looking for more information look to MuscleandFitness.com and Bodybuilding.com both good resources with Demo videos and articles. And remember not everyone develops the same way.

There is also the book _New Rules of Lifting for Women_. It has been a good read for me.

Try finding an online version of "Starting Strength" by Mark Rippetoe, it's a lot to read, but it gives a lot of useful tips on how to perform exercises and how to incorporate them into your work out

^ This, even if you choose a different program I suggest you read this book anyway. the program is quite similar to stronglifts 5x5 anyway.

I'll use curling as an example:

Personally I am currently working out with 35 pound dumbbells and I am doing 3 sets of 8. Now how did I get there?
I started out doing 3 sets of 8 reps with 25 pounds.
I just kept gradually increasing reps and sets over the course of 2 weeks till I could do 5 sets of 15 reps with 25
Then I went to 3 sets of 8 reps with 30 but I always tried to get in that 4th set or get to that 9th rep.
Eventually I built up to 5 sets of 15 reps with 30 pounds. Took about 2 weeks again.

I just kept repeating that cycle and now I am trying to get to the point where I can do 5 sets of 15 reps with 45 pounds.

I apply this method to pretty much every workout in the gym.

Other things to consider when starting out:

If you pick up a weight at the start and you are already able to do 8 sets of 20 reps or something like that I would say that the weight is too light for you and you are ready to move past that weight already. There are people who actually focus on high rep low weight workouts for specific sporting events where all that matters is their muscular endurance but unless you take part in juggling competitions I doubt that is going to be your focus.

If you pick up a weight and you can barely finish 3 sets of 4 reps then you might want to consider using a lower weight but not necessarily. I have worked out with people who focus their whole workouts around lifting very heavy weight for a much smaller number of reps. Some people prefer it in fact. They don't really ever do more than 4 reps but they are pushing weight that is much heavier.

I personally don't recommend that for someone that is just starting out because I think for a novice it could have a higher chance of causing an injury. After you get settled in to a routine and you get to know your own body you will know what you are comfortable with. You can then start to tailor your workout around the specific goals that you have in mind.

EDIT: I forgot that you asked about machines as well. I like the way cwolfman13 put it really. Machines are not by definition bad. In fact when it come to isolation they can often times be your best option. I find this is especially try for leg muscles. That said the machine is basically not necessary when you start out because there really isn't a lot of need to isolate right away. You want to get used to stabling a weight yourself at the start and only go over to machines after you have mastered that.

That's good advice on the machines, thanks!

Cost is a prohibitive factor for me in getting a personal trainer, so I want to see how much I can do without spending any more money than my gym membership. I'm sure it'd be a big help though, so maybe someday.

I'm also a tad intimidated about going over to the "guy" section of the gym and looking like I don't know what I'm doing :P

I know the feeling...I was doing front raises with 5# dumbbells this morning and some guy was doing bicep curls with 30#...I had done mine with 10# earlier. Honestly, there are a lot of muscle bound guys in the weights area at my gym, but they don't bug me any. Since I've been doing dumbbell work for about 6 months now, I get nods, smiles, and the occasional comment from the guys.