The Like operator is a very powerful pattern matching tool that has been heavily optimized for the types of comparisons it does. However, some of those comparisons may not be relevant to the data that you have stored. In particular, Like knows how to correctly match interesting single and double byte matches (such as ß with ss) as well as simpler 'e' with 'é'. If you do not store any such characters in your data, then you might consider using other string operators such as InStr().
Although this won't work for all pattern matching requirements, those where it can be used are worth benchmarking in your application. You may even find that you can use simpler string functions such as Left() or Right() for further performance gains, although Like does recognize some of those and special case them already.
Warning Don't substitute Basic specific string functions such as InStr() or Left() for queries against ODBC data. Because many ODBC servers may not support these functions, using them may cause all data in the query to be brought to the local machine so that the operators can be applied locally. This will be much slower than having the server perform the Like operation on the server. If in doubt, try it and see. The performance difference will be dramatic on large tables.