Traditional VB I/O method...
Dim hFile as Long
Dim sLine as String
hFile = FreeFile
Open "c:\Whatever.txt" For Random As #hFile
Do Until EOF(hFile)
Line Input #hFile, sLine
'... Process sLine
Loop
Close #hFile
There are also more up to date methods such as TextStream objects whixh are a little easier to use, but no more efficient on the whole.
You can get a TextStream object by setting a reference to the "Microsoft Scripting Runtime" library. After creating a new FileSystemObject, use the OpenTextFile method to open and manipulate your file.
If you're used to using ADO, it offers a Stream object that can be used to do the same sort of things. It's character set aware, and can fix issues such as Chr(13) being used to end lines rather than Chr(13) & Chr(10) automatically. But all this added functionality can make it trickier to use.