Commercial leases are nothing like residential ones. For the most part, it's "renter beware" when it comes to commercial leases. As a business owner, the law generally presumes that you're savvy enough to avoid getting stuck with a bad lease.
1. Improvements and alterations
This part of the contract discusses two important things: how the landlord is supposed to fix up the space before you get there and what right you have to make changes later. Make very certain that you understand your limitations. For example, you don't want to go knocking down walls without the right.
2. Use clauses
How you plan on using your space is often part of the deal. You generally aren't free, for example, to convert your space from a specialty store to a restaurant. You may also, however, be confronted with "exclusive use" clauses that seek to limit you in other ways. (Alternately, you may want the right to restrict other tenants around you from competing directly with your business through an exclusive use clause of your own.
3. Subleases and terminations
What happens if you go out of business? Maybe you decide you just hate the grind of running your own company and would rather work for someone else. Maybe the economy has a hiccup that deflates your industry. Whatever the cause, you want to know if you can sublet your place for the remainder of your lease or terminate your lease entirely.
Commercial lease negotiations are hard. It's wise to have an experienced attorney on your side to protect your interests.