Push-ups are a wonderful! They work your chest, arms, shoulders, abs, legs - it's a great core-exercise. You can do them pretty much anywhere without fancy equipment. They don't take up a ton of your time. I could go on about the benefits of push-ups...
My current personal goal is 100 "girlie" push-ups a day. After I get that down, I'll do less reps, but regular push-ups. If you haven't been exercising, it's important to have realistic goals or else you'll get frustrated and quit. But here's something I learned and it helps me do a ton more push-ups in a set than I would without it.
Instead of counting, I say out loud, "I Love You Jesus!"
That phrase gives me a five count using each syllable: I - Love - You - Je - sus! I say the phrase 3 or 4 times and BOOM, 15 or 20 push-ups done. I do about four sets of those for the day and increase as I can.
"I Love You, Jesus!" push-ups help me increase my reps. I pray it can do the same for you. Let me know...