Speed up code and stop screen flickering:

Sub NoScreenRePainting()    Application.ScreenUpdating=False　　'Your code here.    Application.ScreenUpdating=TrueEnd Sub

Preventing calculation while executing code:

Sub NoCalculations()　　Application.Calculation = xlCalculationManual　　'Your code here.　　Application.Calculation = xlCalculationAutomaticEnd Sub

Speeding up code if you have Worksheet or Workbook Events. Also stops endless loops in Events

Sub StopAllEvents()　　Application.EnableEvents = False　　'Your code here.　　Application.EnableEvents = TrueEnd Sub

Use the With Statement when working with Objects.

Sub WithARange()　　With Range("A1")　　　　.Value = 100　　　　.Font.Bold = True　　　　.Interior.ColorIndex = 6　　　　.Copy Destination:=Range("B1")　　End WithEnd Sub

Use VbNullString instead of = "" When needing to default a String variable back to it's default of "" use:

Sub EmptyText()　　Dim strWords As String　　strWords = "Cats"　　MsgBox strWords　　strWords = vbNullString　　MsgBox strWordsEnd Sub

Inserting a Relative formula into a range of cells: Faster than AutoFill or Copy.

Sub NoAutoFillOrCopy()　　Range("A1:A200").FormulaR1C1 = "=SUM(RC[1]:RC[5])"End Sub

Tip: To get a formula, type it in any cell then select the cell, go Tools>Macro>Record new macro and record a macro pushing F2 then Enter.

Avoid the use of Copy and Paste whenever Possible:

Sub NoCopyAndPaste()　　'Instead of:　　Sheet1.Range("A1:A200").Copy　　Sheet2.Range("B1").pasteSpecial　　Application.CutCopyMode=False'Clear Clipboard　　'Use:　　'By-passes the Clipboard　　Sheet1.Range("A1:A200").Copy Destination:=Sheet2.Range("B1")　　'Or, if only values are needed:　　Sheet2.Range("B1:B200").Value= Sheet1.Range("A1:A200").Value　　'Or, if only formulae are needed:　　Sheet2.Range("B1:B200").Formula = Sheet1.Range("A1:A200").Formula　　'See also FormulaArray and FormulaR1C1 etc　　'Instead of:　　Sheet1.Range("A1:A200").Copy　　Sheet1.Range("A1:A200").PasteSpecial xlPasteValues　　Application.CutCopyMode=False'Clear Clipboard　　'Use:　　Sheet1.Range("A1:A200") = Sheet1.Range("A1:A200").ValueEnd Sub

Always declare your variables correctly!

To quickly view a variables definition:
Select the variable that you want the definition for.
Go to View>Definition (Shift+F2)

To return to your previous position:
Go to View>Last Postition (Ctrl+Shift+F2).

Release memory from Object variables:

Sub ReleaseObjectMemory()　　'Could be any variable of the Object type　　Dim wSheet as Worksheet　　'Set Object variable　　Set wSheet = Sheet1　　'Your code here.　　'Release memory　　Set wSheet = NothingEnd Sub

Don't get caught in the Loop.
Follow this link to see why Loops should (and usually can) be avoided.

Avoid If, Else whenever possible

More often than not people would use an If, Else Statement to test whether a condition is TRUE or FALSE. There is however a slightly faster (and less typing) method. The first example shows the common method, while the second shows a faster method. Of course in such a small example the difference is not noticeable.

Sub TrueOrFalseSlower()　　Dim bYesNo As Boolean　　Dim i As Integer　　If i = 5 Then bYesNo = True　　Else    bYesNo = False　　End If　　MsgBox bYesNoEnd Sub

Here's a better way!

Sub TrueOrFalseFaster()　　Dim bYesNo As Boolean　　Dim i As Integer　　bYesNo = (i = 5)　　MsgBox bYesNoEnd Sub

Another common need is to toggle a variable between True and False depending on a condition. For example:

Sub ToggleTrueOrFalseSlower()　　Dim bYesNo As Boolean　　If bYesNo = False Then    bYesNo = True　　Else    bYesNo = False　　End If　　MsgBox bYesNoEnd Sub

Here's a much better way

Sub ToggleTrueOrFalseFaster()　　Dim bYesNo As Boolean　　bYesNo = Not bYesNo　　MsgBox bYesNoEnd Sub

Source: http://www.ozgrid.com/VBA/SpeedingUpVBACode.htm