How to create login and logout trigger for client audit?
You can add a simple IF statement to your LOGON trigger, as such:

USE test;
GO
CREATE TABLE LogonAudit
(
    AuditID INT NOT NULL CONSTRAINT PK_LogonAudit_AuditID 
                PRIMARY KEY CLUSTERED IDENTITY(1,1)
    , UserName NVARCHAR(255)
    , LogonDate DATETIME
    , spid INT NOT NULL
);
GO
GRANT INSERT ON Test.dbo.LogonAudit TO public;
GO
CREATE TRIGGER MyLogonTrigger ON ALL SERVER FOR LOGON
AS 
BEGIN
    IF SUSER_SNAME() &lt;&gt; 'sa'
    INSERT INTO Test.dbo.LogonAudit (UserName, LogonDate, spid) 
            VALUES (SUSER_SNAME(), GETDATE(), @@SPID);
END;
GO
ENABLE TRIGGER MyLogonTrigger ON ALL SERVER;


This will only audit logons for users not named 'sa' by virtue of the line IF SUSER_SNAME() &lt;&gt; 'sa'

Alternatively, if you want to ONLY audit the login of a specific user, you could write the trigger like:

CREATE TRIGGER MyLogonTrigger ON ALL SERVER FOR LOGON
AS 
BEGIN
    IF SUSER_SNAME() = 'SomeUser'
    INSERT INTO Test.dbo.LogonAudit (UserName, LogonDate, spid) 
            VALUES (SUSER_SNAME(), GETDATE(), @@SPID);
END;


This will only record when SomeUser logs into the server.