Procedures are different to UK - so use an experienced bi-lingual professional.
Determine the requirements and then visit.
Don't be misled by apparent cheapness. Renovations and conversions can be expensive - more so because in general properties are far larger than in UK.
Always negotiate - there tends not to be market values, as properties vary so much.
Ascertain the TOTAL cost of purchase - determine ALL fees/taxes and responsibility for payment. Agency fees/government taxes are at a far higher level than UK - allow 12 - 15% as an approximation. Local French agent will advise more exactly on specific properties.
The initial contract (there are different forms with differing consequences, but the usual one is a "compromis") is the important document. Ensure relevant condition clauses (e.g. does transaction depend on getting a loan?) are included. Once signed, and conditions met, (and definitely with a "compromis") YOU MUST complete.
Need for deposit 0 usually 10% - on initial signing. Be careful this could be forfeited if deal not completed.
Any special requirements to observe? French inheritance laws very different and repercussions can be significant.
Generally all French agents/notaires will take you to the properties. They must all be registered, financially bonded and in possession of a mandate for the properties being sold.
Legal position - generally one notaire acts for both vendor and seller. He is obliged to act impartially. You can request a separate notaire at no extra cost (Statutory fees split 50/50). Very rarely used except in large complex transactions.
Note in general French property details can be very sketchy - the approach has always been that a serious buyer will make the effort to visit the area and see a range of properties.