can i work out everyday:
what are you doing? usually its fine as long as you not doing heavy weight low rep everyday, puts you at risk of injury. Studies have shown that working out everyday does not hold a huge amount of benefit over a few intense sessions a week, but i'll have to look up the article, and sports science, well, isn't usually more anecdotal than hard evidence.
Cardio: everyone i know says 20 mins plus or you get little benefit
Weights and cardio on the same day: i know people who do but i have never been to bothered, my friends who do it, do it for weight loss
Eat balanced but you might wanna add some extra carbs, protein shakes are good for the extra calories, but tbh usually you get enough protein in an average diet just good to have some around in case you have a light lunch or post workout.
have been using bodbot lately as to experiment/ and it also has a whole heap of different exercises with video links, definitely a good place to start until what you know what you are doing
my personal tips for weight training:
watch your recovery times, i really feel the benefits if i keep them strict
get a mate, helps you push yourself to your limits and useful as a spotter
free weights, avoid machines, you don't wanna be isolating muscles unless you're bodybuilding or 'rehabbing', you wanna make your muscle useful so concentrate on exercises which work a range of muscles (pullups>bicep curls, bench press, squats, deadlifts, renegade row, yltw fly, lunges..to name a few)
find exercises which you enjoy, to do when you lack motivation (any workout is better than skipping a day, but try and be as strict as possible with yourself)
switch things up as much as possible: every few weeks find a different set of exercises to do go between high and low rep, fast and slow, to challenge your body as much as possible (again bodbot is fantastic for this)
posture is key to good technique, nearly everyone i see can improve posture
don't push an injury you'll regret it
GOOD TECHNIQUE IS ALL IMPORTANT, THOSE MIRRORS AREN'T FOR POSING
PS: i read recently that crunches/sit ups are pretty bad for your spine
PPS: all this advice is through my own reading/experience, you'll find you end up doing a lot of research to optimise your workout plan