One of the most difficult learning curves for a novice weight lifter to tackle is weight. Lifting too much, too early may cause injury and prevent adequate muscle recovery. Lift too little, and you won't progress. The problem is that every lifter is different, so there is not a uniform answer - even for basic routines such as lateral or front raises. Consider several factors that go into successful weight training to determine how much weight you should lift while doing front and lateral raises.
Form is crucial to success. Lifting less weight than you can support while still getting the form precisely correct will let you progress much further than if you simply swung around too much weight indiscriminately. Both exercises work the deltoids and the trapezius in slightly different ways. The motion for each exercise should be slow and methodical, with your arms locked straight. Don't swing away to generate momentum. If you have to do that to perform your reps, you're trying to lift too much weight.
The most amount of weight you can lift for any one exercise is a variable number. To understand how much you lift for a set of 10 reps, you need to determine your max capacity. This is the most amount of weight you lift for two full reps before failure. The only way to determine max capacity is trial and error, but that doesn't mean starting at zero. For lateral and front raises, take the amount of weight you would use for a dumbbell biceps curl and divide it in half. Use this as a baseline only. Try one rep. If it's too easy, go heavier, or if you can't complete the rep, go lighter.
Weight versus Reps
Weight lifting isn't just about lifting as much as you can for all exercises in all situations. Some lifters use lateral raises as a warming exercise in between bench press sets, and front raises as a warming exercise in between shoulder press routines, but only with 5- or 10-pound weights. Other lifters don't want to bulk up, they want to increase muscle endurance. This requires multiple sets of exercises performed with low weights for a lot of reps. For example, a max lifter may do three sets of eight to 10 lateral raises with 30-pound dumbbells, and an endurance lifter would do five or more sets of 20 reps with 10-pound weights. Don't be afraid to use less weight if you increase the number of reps.
No matter how slow and methodical you perform your reps, there is always a risk of injury, and this risk increases when you attempt to lift more than you can handle. The type of equipment you use to perform your reps matters. For either exercise, you can use dumbbells, free weight plates, kettlebells or even milk jugs filled with sand, but the safest option is usually the one that best conforms to your grip. A kettlebell or a dumbbell allows you to have a strong grip on the free weight through the entire motion, while a free weight plate does not.