1) 整数除法运算符 \ 和 /
\ 比 / 快10倍 （如果是整数除法并且不需要保留小数）

(2) 赋值运算符 a +=b 和 a = a+b
+= 快

(3) 串联运算符 & 和 +
用 & 快

（来源：http://www.devcity.net/newsletter/archive/devcity/devcity20040315.htm#ni030)
.NET Pro: Optimize the Performance of VB.NET Applications
Operators

by Mike McIntyre

Division: \ V.S. /

Divide integral values with the \ (back slash) operator when you do not need decimal points or fractional values. The \ operator is the integral division operator and it is up to 10 times faster than the / (forward slash) operator.

Compound Assignment Operators: a += b V.S a = a + b

Compound assignment statements first perform an operation on an argument before assigning it to another argument. Example:

a += b

In the example above, b is added to the value of a, and that new value is then assigned to a. Compound assignment operators are more concise than their constituent operators (separate + and =). Compare the statement above to the one below. The statement above is a shorthand equivalent of the statement below.

a = a + b

Compound assignment operators are faster. If you are operating on an expression instead of a single variable, for example an array element, you can achieve a significant improvement with compound assignment operators.

Compound assignment operators for numbers:

^=
*=
/=
\=
+=
-=
Compound operator for strings: &= Example:

Dim a As String = "First " a &= "Name"
Result: First Name

Concatenation: & V.S. +

Use the & concatenation operator instead of the + operator to increase the speed of concatenations. Performance of the & and + operators are only equivalent if both operands are type String. If not, the + operator is late bound and must perform type checking and conversions.