Subjecting yourself to critique and criticism is a great way to learn about your photography and yourself. I think you need to go beyond showing your photos to your parents and grandparents. These folks love you and think everything you do is great. They are going to pat you on the head and heap praise upon you. This may give you nice, warm feelings, but probably won't be the most constructive advice you receive. There are groups and websites that have very formal sessions and criteria checklists they use to critique submitted work. I have participated and judged at a few of these events. The judges give very specific details to explain their opinions. If you enjoy that sort of thing, have at it. They tend to be a little stiff and overly-serious for me, but these groups have their place. You may not always like the way they dissect your pretty flower photo, but you will get information you can use.
Most of the time, however, my preferred method of critique is a group of friends discussing the our latest images and giving and receiving feedback. The environment is relaxed and safe. There is nothing in jeopardy in this setting. We are just looking for opinions, suggestions, and different points of view. You may see your photo in a new light.
Feedback is more than "I like that photo." There are several things to keep in mind when you give feedback: give specific descriptions of your likes and dislikes; what are the technical characteristics of the image that are successful; what needs work; try to give suggestions to improve any perceived weaknesses.
What else can you say? How about: this is a nice, natural portrait with even lighting. The little boy is relaxed and comfortable with you, which led to a facial expression that doesn't look posed. The colors are complimentary and add punch to the scene. The blue stucco provides a nice background, is repeated in his eyes and shirt. (BUT....) You might use a wider aperture for a shallower depth of field, or, maybe, try a slight blur effect to the stucco to focus all attention to the boy. This looks like it was taken in a shaded location, so you might have used a reflector or very light fill flash to put slightly brighter highlights in his eyes. With this type of information, you get helpful information to use next time you shoot this type of shot.
Don't be afraid to say you don't like a shot, but use terms that won't offend. Offer advice about what you would do differently and why. Ask the photographer to tell you her intent in the photo. You might think it's too dark, but she may have wanted it dark for a reason.
If your work is being critiqued, don't get offended or defensive - they're not attacking you personally. You can't learn much if you get your feelings hurt, and, if you're in a critique session, you came for an honest critique, not vapid praise. You and your fellow photographers may not always agree on a picture, but that's fine, too. The appreciation of photography is a subjective thing. Sometimes one of your favorite photos may not strike a chord with your viewers.
I like this umbrella picture. I like the double set of lines, radiating outward; I like the circle of cloth where the seams join at the top; I like the chain that interrupts the otherwise consistent rhythms of the image. I saw this image before I put the camera to my eye, and it matches what I envisioned. Most of my photographer friends just don't appreciate this image (I really think I need some friends with better points of view). I still have a big print hanging of this image, despite their indifference!
The important thing is to show and discuss your work. Surely, you're not spending all this time with photography so you can fill up a hard drive with unseen image files? Find people whose opinions matter to you and who have enough knowledge to assist you in your drive to improve. Your photography will benefit from the experience, and you will have more fun pursuing it.