What camera lens should I use?

So I have a photography gig, at my friends bands concert but I'm a bit of an amateur. I have the Nikon d3100, and I have the standard lens and the VR zoom. Could I someone tell me which lens would be best to use?

Do Canons and Nikons have the same size hot shoe?

I'm getting a Nikon camera, but was originally planning on getting a Canon. The Nikon D3100 and the Canon Rebel T3 to be exact. Are the hot shoes on these brands/models the same size, so that I can get the same external flash I picked out for the other camera?

Using a third-party flash on a nikon d90?

I'm interested in buying a certain third-party flash for my d90. The flash can zoom, tilt, rotate and has a diffuser built in. The flash has only one button on it which is the on and off switch. It doesn't have an lcd, but it does have a sticker with a bunch of numbers (it's a manual flash). I would have given a better description of what was on the sticker but I was in a hurry so I didn't have time to read the sticker.

I'm not sure what the name is. It's not a big brand like nissin or yongnuo.

So what I'm wondering is: Can my camera control the flash? I read somewhere that you can't control third party flashes from your camera so I want to double check.

And what are the pros and cons of buying a third party flash?

I know that someone is probably going to tell me to buy a nikon flash, but I can't afford it at the moment. I will be getting one in the future.

Added (1). @John P

I did ask the sales person about that, and he said that it won't fry the camera.

Why do my RAW to JPEG conversions look darker?

Ok, they don't "look" darker, they are! Putting my 2 images side by side, the raw file that i edit to my wants looks perfect, when i save it as a jpeg and open it, it comes out considerably darker and less "smooth" (looks more rough-ish). Why does this happen? I'm new to this dslr stuff but i don't get why my images come out with less quality, it's very frustrating! I take pictures of food for a blog i'm starting and i want my images to be unchanged when i post them but the jpeg looks worse in quality. Is there any way i can keep the quality i see in raw after it gets converted? Should i just shoot in JPEG as opposed to RAW if converting is going to undo my editing anyways? Some help would be greatly appreciated.

also, just in case, i have a nikon d3100 and i edit my raw files in adobe photoshop cs6.

How to set picture control on my nikon d3100?

Okay so on my nikon i'm trying to adjust the picture and i went to the shooting menu and the set picture control button is gray and when i click it, it says "this option is not available with current settings" How do i fix this?

What type of fisheye lens do I need?

I've got a Nikon D5100 with the stock 18 to 55mm lens. Basically what I'm wanting is the peephole effect, you know where its like a round image that looks like you are looking through a peephole, and it's kind of like a bubble effect. I want one of the lenses that just screws onto the current lens that I have, but all the fisheye lenses I find are for far away wide angle photos, I want the bubble effect, not a long wide angle. How do I achieve this and what lens do I need?

Added (1). Okay but how do I adjust the camera to where the shot is in a circle instead of a rectangle, do I need to zoom way out, or adjust the settings of the camera?

What camera settings do I use to photograph one of my paintings?

I have a Nikon D5100 and an oil painting that just finished drying. What kind of manual settings would work best to get the color and such right? Also should I use flash or go outside on a sunny day? A cloudy day?

Going on vacation, what lens is good for my DSLR?

I'm going to italy for one week, and i'm looking for a lens for my nikon D90 that's not too heavy that i can shoot some nice landscapes with and just the basics. Currently i have a very big lens on it and i didn't take it on my last vacation because it was a pain in the a** to carry it around all the time.

New York City Photography?

Tomorrow I'm going to New York City and I'm bringing my Nikon d3100. Do you guys have any tips for shooting in New York City? I'm going to go on top of the Empire State Building (I believe at night) will i need a tripod to capture good pictures? I will also be taking pictures of Times Square. Any tips?

Should i shoot in raw or jpeg?

So tomorrow is my birthday and i'm getting the nikon d3200 (with 18-55mm kit lens), the camera has a 24mp sensor so the files will be large anyway. I know the quality is better and the flexibility of a raw file is greater however a raw file of 24mp will take up a lot of memory (around 50-60mb i think).so should i sacrifice the quality and shoot in jpeg to allow more photos. Or should i buy an external hard drive/usb to save raw files onto instead. And could someone also tell me what the difference is as well.