8 Tips for beginners
1.) Do compound lifts first. Squats, Deadlifts, Military Press, Barbell Rows, Pullups, Bench Press, Dips. A solid base knowledge with these exercises will take you far already. Isolation exercises are usually beneficial only on special cases. Like recovering from a muscular tear or volume based workouts.
2.) Concentrate your lifts on Free weight exercises. Avoid machines as it doesn't train your muscle for stabilizing. Leave machines to the intermediate bodybuilders. A 300lb bench press on a smith doesn't equate to 300lb bench press on barbell.
3.) Perfect your form first. Better neural response to an exercise is very important. And it also avoids accidents.
4.) Don't waste your money on supplements yet. Focus on your diet; if you're an ectomorph/skinny, eat more and struggle to gain weight every week or every 2 weeks, if you're an endo/mesomorph/fat/athletic, clean up your diet BUT never compromise to the point that you're functioning beyond normal.
5.) Strength gain means muscle gain. Utilize lower reps with high resistance exercises. The harder you work, the stronger you become, the larger you'll grow. More muscle = more fat burn
6.) Remember, muscle pain DOESN'T always equate to muscle gain. It simply means that lactic acid is flushing through your muscles. So tiring your muscle out with uber high rep exercises can actually deteriorate your performance.
7.) Experiment only after you establish a good foundation for your basic compound lifts.
8.) I'm not in anyway discrediting all trainers but choose wisely. Most of them only became trainer after a seminar or so and aren't fully knowledgeable with their field. Choose a trainer that you think really knows what he's doing (In case you're lazy on the research department). One who practices what he preach and his body shows it.
Have fun lifting!