Method:

1. Write down the 8-bit binary number...
2. Assign powers of 2 to each bit position...
3. Multiply each digit by its corresponding power of 2...
4. Add up the products from step 3...

Example:

Let's convert the binary number 10101110 to denary:

Binary number: 1 0 1 0 1 1 1 0
put binary digits in the correct place beneath each power of 2
Powers of 2: 
                    27    26    25    24    23    22    21    20
                    128    64     32     16     8      4      2      1
                    ___________________________________________________
                    1      0      1      0      1      1      1      0
Sum: 128 + 32 + 8 + 4 + 2 = 174

Therefore, the denary equivalent of the binary number 10101110 is 174.
Additional Tips:
You can use a table to organize the calculations, listing the binary digits, powers of 2.