A few things to keep in mind before you begin 

1.  Get checked out
     If  you have any worrier at all about your readiness,get youreself checked by a GB,
     especially if u have a history of heart trouble.

2. Warm-up properly 
     Before doing any of the workouts,raise your body temperature by doing gentlecardio work,
     such as running or cycling,and prepare yourmuscles by doing squats,
     bends and presses.It will help to prevent strains or muscle tears. 
3. Stretch afterwards 
    Stretching helps flush lactic acid out of your muscles,which can prevent some muscle                 soreness.Good flexibility also allows you to work your musclesthrough a bigger range
    of motion,which will help you to get fitter and stronger faster.