When searching for a full body casing, consider the following tips:

1. Compatibility: Ensure that the casing is designed specifically for the Samsung Guru Music 100 model to ensure a proper fit.
2. Material: Look for a case made from durable materials like silicone, TPU (thermoplastic polyurethane), or hybrid materials that offer good protection against drops and scratches.
3. Coverage: Make sure the casing provides full coverage for the phone, including the back, sides, and corners.
4. Port Access: Check that the case has precise cutouts for ports, buttons, camera, and speakers, so you can access all the phone's features without removing the case.
5. Design and Style: Choose a design that suits your preferences, whether you prefer a sleek look, vibrant colors, or a transparent design to showcase the phone's original aesthetics.
6. Reviews and Ratings: Before making a purchase, read reviews and check ratings from other customers to get an idea of the quality and durability of the casing.
7. Brand Reputation: Opt for well-known and reputable brands for a higher likelihood of quality and accurate fit.
8. Additional Features: Some cases might come with extra features like built-in kickstands, card holders, or screen protectors. Consider whether these features are important to you.

Remember that my information is accurate up until September 2021, so I recommend searching on current e-commerce platforms or contacting local electronics stores to find the most up-to-date options for a full body casing for your Samsung Guru Music 100.