SQL Server 2008 Installation pointers for optimizing Performance and Scalability
It is SQL Server 2008 or SQL Server 2008 R2 ?? Because in your question you mention that client want to upgrade from 2005 to 2008 R2 and you're asking about migration from 2005 to 2008. So for sake of answer I am assuming it is 2008 R2

Since you will not be using other services like SSRS,SSAS and SSIS it should make you like a little easy. Some suggestions are,


Use separate physical drives for data and log files for all user DBs
Separate physical drive for temp db, backups,system dbs
Aligned drive partitions (however it should be taken care by itself since you are using Win 2008 R2 but better check 'em) 
Setup proper auto increment based on your expected growth
Proper recovery mode (Full recovery mode is recommended)


Actually you can find loads of tips for SQL Server database server configuration. Following links can give you some help. 
For SQL server 2005/2008 (but can be used for 2008 R2)
Or General MSDN help for SQL Server 2008 R2
Or google for "SQL Server best practices", which can be of different categories like installation, dev, security configuration, administration, migration etc. But I really doubt that you will find all-in-one type of solution somewhere because in most of the cases it really depends on your requirements.