Your question boils down to auto vs manual focus. From the methodology you've described, it seems that you are attempting to use autofocus to get a picture of the night sky. That's not a great plan because the objects your camera can focus on in the night sky are pretty small points of light, and autofocus usually only works well under brightly lit conditions. You do have a couple of options though, both with and without auto focus.

Regardless of if you're going to attempt auto or manual focus, the fist thing you'll want to do is spin the dial to M mode. If you let the camera guess your exposure at night, you're unlikely to be happy with the results.

If you want to keep using auto focus you have a few option. The first thing you'll want to do is set your AF point selection to manual mode and select a single point. A quick google for your specific model should tell you how to do this, but you should end up somewhere in the menus that looks like the below image.

You'll also want to set your AF mode to One Shot. This is likely set in a very similar way to the AF point selection above. This will keep the camera's focus locked once you set it. If you have it set to the other modes the camera will attempt to adjust the focus as you move your camera from one object to the next, which is precisely what we're trying to avoid.

Now aim your camera at a far away bright object, like a street lamp way at the end of your road. Line the object up under your focus point and press your shutter button half way and then hold it. Your focus should now be locked, and as long as you keep the shutter held halfway down it shouldn't move. You may now leisurely point your camera at the sky and fully depress the shutter release to take your picture. If you're using a tripod though, which you should since you're asking about long exposures, this may be a little difficult to pull off without taking a few accidental pictures on the way to repositioning the camera towards the sky.

Another option very similar to the last is to use the AE Lock button on the back of your camera to focus the distant object, instead of the half shutter press. See the below image for its location. You'll probably have to perform some setting in the menu of your camera to get this to work since by default this button locks exposure instead of focus, so again a quick google search for "rebel back button focus" will be your friend.

A final autofocus option is to use either of the above options to focus on your distant object and then switch your lens to manual focus. First thing you'll want to do is look at the left side of your lens (if it's attached to the camera, see image below). Here you should see at least one toggle switch with something like M on one side and A on the other. M stands for manual focus and A stands for autofocus. Right now it should be flipped towards A. This time, after you've focused on your distant object release your focusing button and the flip the switch in the side of your camera to M. Congratulations, you're now in manual focus mode and your focus point is locked unless you change it. You could use your remote to take a picture using this method or any of the methods I'll describe below.

The problem with any of the above methods is that you're approximating your sky focus point (at infinitely) with something that is potentially much closer. This means there is a good chance that after you attempt any of these methods you may still end up with your sky photograph out of focus. This is why I would highly recommend manually focusing on the sky itself.

To do this, start out by flipping the toggle on your lens to M. Now that your lens is in M mode you have to set the focus point manually. Somewhere on the lens is a focus ring. I'm guessing it will be at the far end of your lens, right next to the glass like in the photo above, but it may also be in towards the camera body. If you're using a zoom lens it's going to be a ring that is considerably smaller than the one that zooms the lens. Point your camera at the sky and spin this ring to one of it's stopping points. If you spin it in the direction of infinity your stars should be pretty close to small points of focused light. If you spun towards the near focus end of the focus range they'll be large, diffuse balls of light. If that's the case spin to the other extreme of the focus range.

Now that you're focused at infinity, start spinning the focus ring in the only direction it can go. You'll need to play with the focus a little around this range until you get the sharpest stars you possibly can. If you have live view on your camera I would highly recommend using it here. While in live view use the live view 100% zoom to blow up your sensor's image and point your camera at a bright star. Then use the focus ring to make this star sharply in focus and you should be all set.

Now all you have to do is play with the exposure settings, or look up some starting points online, and you'll be taking focused, long exposure night photographs in no time.