Lisa - Both Teri and Gwenn have provided good information.
To elaborate a little more to what they stated - An FHA appraisal and conventional appraisal are done basically the same. Comparables (sold and active) are chosen by research based on similarities, location, and time frame. Time frame consists of the most recent sales, location consists of the closest to the subject property, and similarities consists of (exact - closest to - similar) square footage, age, construction, room count, bedroom count, bath count, amenities, condition, lot size and usage, location.
An FHA appraisal requires more visual inspection of the property to meet FHA guidelines and requirements for Safety - Security - and Soundness. Here is a link that details an FHA inspection - APPENDIX D: VALUATION PROTOCOL http://www.hud.gov/offices/adm/hudclips/handbooks/hsgh/4150.2/41502appdHSGH.pdf - it's 139 pages in PDF format. It is also part of the FHA Handbook 4150.2 for appraisers - link to sections of handbook - http://www.hud.gov/offices/adm/hudclips/handbooks/hsgh/4150.2/index.cfm .
Here is another link that has Mortgagee Letters with information that may be of interest - such as Max Mortgage Limits, Second Appraisals, Lender Accountability, Repair and Inspections - http://www.hud.gov/groups/appraisers.cfm
An FHA appraisal will generally cost more than a conventional due to the additional work and time involved and it is best if you pay the appraiser directly (at time of inspection) due to the fact that many lenders lately have been inflating appraisal costs on closing docs for more than what was actually paid. You are also entitled to a copy of the appraisal but you have to request it in writing from your lender since USPAP regulations prohibit appraisers from providing a copy (or discussing) to anyone except the client who ordered the appraisal regardless of who paid for it.