To begin with workouts, figure out what makes YOU happiest. Maybe you actually enjoy a nice run to get lost from all of that work you have to do at home. Maybe you jump around from different machines because you cannot wait to dive into all of those in front of you! Maybe the gym you chose has a pool and you would rather swim off your cardio than run straight for an hour on a treadmill. Start the first week off trying anything and everything to find what you like best - but remember to take one day at a time.
If you ultimately started at a gym to lose weight, cardio will become your new best friend :) Try doing a series of different machines instead of sticking to one. Set yourself distance goals and try to go a little bit further each day. The treadmill is great for warming up and cooling down for the beginning and ends of your workouts. The elliptical is great for seeing how long you can move without stopping. Maybe throw in a bike ride and see how many miles you can go before you feel like you are going to pass out. Stick to the cardio first, and then worry about toning up your body later.
Now, if you are already at the point where you look in the mirror at your fabulous self every morning, thinking: Look at that body! It's perfect...except my skinny arms and chicken legs could be a little bigger - then the machines are for YOU! Start targeting the same muscle groups one day at a time. Try doing all back machines one day and then all leg machines the next. Consistency is key! Remember to rotate your groups each week, trying to touch everything in one week and then back on the same routine next week. Make your body have something to look forward to. Arrange a fun schedule for you to follow each week:

Tuesday Back Toning
Wild Weights Wednesday (this would be your choice each week)
Thursday Shoulder Throw-Down
Friday Fun-Runs!
Saturday: sleep in?
Whatever your new schedule may be, remember to stick with it and have fun with it!
Cheers!
Meg
Image Credit: http://shannonseeley.blogspot.com/