1. You may use 0.5 mL of 5% (w/v) aqueous phenol and 2.5 mL of sulfuric acid with 0.5 mL of appropriately diluted sample.
2. Appropriate dilution of the sample will depend on the carbohydrate concentration. You will have to determine this empirically (i.e., by trial and error).
Measuring carbohydrates by phenol-sulphuric acid is quite tricky and tedious. Particularly for the handling of conc. sulphuric acid. Using smaller volume of reagents like microplate format should be a preferable method. The following is good reference article : Analytical Biochemistry 339 (2005) 69-72. Good luck!