The scene you are shooting is too extreme for your camera. The dynamic range is too great.

There are several possible ways to deal with it.

One way is to take two photos... one exposed for the sky, the other exposed for the foreground. Later you can combine the "correct" portions from each in post-processing software (such as Elements or similar).

Another way is to use a Graduated Neutral Density filter... which is half gray, half clear. ND Grad filters come in various strengths... you probably need at least two stops, maybe three. The best type are rectangular and slide into a filter holder that screws onto the front of your lens (Cokin makes a fairly inexpensive set, adapters and filter holders... there are more expensive from Lee, Singh-Ray and others). With this type filter you cover the brighter sky with the gray area of the filter to "hold back" some of its brightness and let the foreground show through the clear portion of the filter. This method isn't as precise as the above, two-shot method, but could work pretty well with your examples.

A third method is to use a flash or several flashes to illuminate portions of the foreground, but that wouldn't work very well in your examples. It works best when there's some foreground objects fairly close.

There really isn't much foreground in your first example image, and the silhouette of the trees in the second one actually look pretty good (plus would be relatively hard to correct now... or using the filter method mentioned above). So I did some adjustments to the foreground in your third shot, using Photoshop. First I created a layer and adjusted the brightness of the foreground strongly, but that caused the sky to be "blown out"... So I used a mask and removed just the sky portion, allowing the background sky to show (unadjusted) through. It's similar to the method of taking two shots, but there's a limit to how much can be done trying to do it all this way with post-processing adjustments. It's also limiting working with JPEGs such as these. RAW files have more latitude for adjustment. Image noise and artifacts increased a lot, so I had to apply some noise reduction. I also had to do some hand blending right at the horizon line, then flatten the two layers into a single image. It's pretty subtle, still... but there's a bit more detail in the foreground now, especially when you view the full size image.

The scene you are shooting is too extreme for your camera. The dynamic range is too great.

There are several possible ways to deal with it.

One way is to take two photos... one exposed for the sky, the other exposed for the foreground. Later you can combine the "correct" portions from each in post-processing software (such as Elements or similar).

Another way is to use a Graduated Neutral Density filter... which is half gray, half clear. ND Grad filters come in various strengths... you probably need at least two stops, maybe three. The best type are rectangular and slide into a filter holder that screws onto the front of your lens (Cokin makes a fairly inexpensive set, adapters and filter holders... there are more expensive from Lee, Singh-Ray and others). With this type filter you cover the brighter sky with the gray area of the filter to "hold back" some of its brightness and let the foreground show through the clear portion of the filter. This method isn't as precise as the above, two-shot method, but could work pretty well with your examples.

A third method is to use a flash or several flashes to illuminate portions of the foreground, but that wouldn't work very well in your examples. It works best when there's some foreground objects fairly close.

There really isn't much foreground in your first example image, and the silhouette of the trees in the second one actually look pretty good (plus would be relatively hard to correct now... or using the filter mehod mentioned above). So I did some adjustments to the foreground in your third shot, using Photoshop. First I created a layer and adjusted the brightness of the foreground strongly, but that caused the sky to be "blown out"... So I used a mask and removed just the sky portion, allowing the background sky to show (unadjusted) through. It's similar to the method of taking two shots, but there's a limit to how much can be done trying to do it all this way with post-processing adjustments. It's also limiting working with JPEGs such as these. RAW files have more latitude for adjustment. Image noise and artifacts increased a lot, so I had to apply some noise reduction. I also had to do some hand blending right at the horizon line, then flatten the two layers into a single image. It's pretty subtle, still... but there's a bit more detail in the foreground now, especially when you view the full size image.