Cardio to compliment heavy lifting! How to?

Hi I am 17 years of age and have been doing gym work for close to 14 months now, I go to the gym 3 days a week (Mon, Wed and Fri) but I wish to get really good abs but I do want the sharp edges. Currently I do training exercises per night at home for my abs and these are as follows:

1. Normal sit ups 10-15 reps

2. I also do an exercise where I lie on the floor and raise my upperbody up and also raise my legs and touch my knees with my elbows (my legs move like I am on a bicycle). 10 reps

3. I lie on the floor with straight legs and raise them to make my body form a 90 degree angle. 10 reps

I do 2 sets of each with about 30 seconds of rest in between. I am not sure what kind of cardio work out I should do to compliment my current training schedule. Oh and I was thinking of purchasing one of those ab work out machines such as the Ab-Swing, is this a good idea? Just wondering because these machines cost $200 and up. By the way I am a pretty lean boy, I have a boxing bag at home and tend to use that every now and again. Can you give me some advice on using the boxing bag to aid my ab sessions and general work out sessions?

I am thinking of changing my work out schedule next year to include my legs, oh and is it a good idea to work every muscle on each day? (Which is what I have been doing since I started) or should I do various body parts on different days? If I should can you recommend me a weekly routine?

Any help given would be much appreciated :D
Thanks

ORIGINAL: Cyclops

Hi I am 17 years of age and have been doing gym work for close to 14 months now, I go to the gym 3 days a week (Mon, Wed and Fri) but I wish to get really good abs but I do want the sharp edges. Currently I do training exercises per night at home for my abs and these are as follows:

1. Normal sit ups 10-15 reps

2. I also do an exercise where I lie on the floor and raise my upperbody up and also raise my legs and touch my knees with my elbows (my legs move like I am on a bicycle). 10 reps

3. I lie on the floor with straight legs and raise them to make my body form a 90 degree angle. 10 reps

I do 2 sets of each with about 30 seconds of rest in between. I am not sure what kind of cardio work out I should do to compliment my current training schedule. Oh and I was thinking of purchasing one of those ab work out machines such as the Ab-Swing, is this a good idea? Just wondering because these machines cost $200 and up. By the way I am a pretty lean boy, I have a boxing bag at home and tend to use that every now and again. Can you give me some advice on using the boxing bag to aid my ab sessions and general work out sessions?

I am thinking of changing my work out schedule next year to include my legs, oh and is it a good idea to work every muscle on each day? (Which is what I have been doing since I started) or should I do various body parts on different days? If I should can you recommend me a weekly routine?

Any help given would be much appreciated :D
Thanks

Um... im ny day we did 150 situps followed by 50 pushups...

You want a recommendation, join a gym, read the routine i posted earlier...

What you do 10-15 situps wtf? unless your head weighs 190 pounds that isn't even enough to get started... you do situps until you cannot lift your back from the floor...

you do pushups until you cannot push up again...

Join a gym...