Depending upon how your firm currently keeps track of the attorney's time will give you insight to the types of packages that are available. Many firms have clients with multiple matters. Not all programs can handle the differences. Many firms have more than one attorney working on the same case. If this is a requirement, then you need to have a time and billing package that will track multiple attorneys per case.
Many clients require a recapitulation, or summary, at the end of their bill.
Many legal software vendors have both available in separate modules. A big factor in larger law firms is ensuring all checks written for a client are tracked on the client's ledger. Many of these systems will print the check for you, enter it into the bank account check register, place it into the correct account of the general ledger and place it on the client's ledger. Then, at the end of the billing cycle, that cost is automatically placed onto the client's statement for billing purposes. The key is one-time entry.