Mine recommended certain pieces, then I made the purchase. I paid her by the hour for her time. In my case, it was a huge waste of money. I'd work with an ID again, but never her. She recommended painters and electricians, and I believe she got a cut for the recommendation.

I think they all work differently, but I was not really happy with the two I worked with--separate projects. If this is for LR/FR/BR furniture...I would work with a designer at your favorite furniture store.

This topic has had lots of discussion on this forum.
Many of the contributors (including me) are or have been interior designers, and the clients of designers who join have had a wide variety of experiences.

Search "interior designer" on this forum and read those threads. I think that will help you.

I meet with the designer and discuss the project. She then emails me various options with prices. Often we meet again to review fabric Samples and make the selections. Most of the time the designer forwards me the invoice and I pay directly. There are some items she has ordered and then billed me. I usually pay in advance since most of these are custom orders. I pay with a cc so am somewhat protected.

Many of the furniture and fabrics I have bought have been through a to-the-trade-only design center. My designers orders through her account and then bills me. My issue is her billing practices. She bills hourly and for furniture/fabrics it is cost plus 20%. The problem is she doesn't itemize her hours and does not show me the cost/wholesale invoice, so I'm not sure what the base is for calculating her 20% profit. I accepted it at first, but as I've gotten more involved, I don't appreciate the smoke-and mirrors feeling I get. Our projects are staring to add up to a very significant amount. I'll finish up my current project and have a discussion to change the contract. If she does not agree then we won't be doing any more business together.

The few times I have used an ID, I have been disappointed. I think if I were to use one again, I would have a clear idea, with inspiration pictures.
Chispa, are you really happy with the results and there is no way you could have thought these things up yourself? in my book then, that would be worth almost any price.

ellendi, I'm very involved in the process and picked most of the things myself, i.e. the ID would bring bags full of fabric samples and I picked one I liked. She is good at being more daring with pillows than I would be on my own. For the current project, I went to the design center by myself and found a fabric I liked and had her use that as the starting point. I'm happy and at a very good point in life that we have the extra money to spend on "pretty stuff", but it isn't worth almost any price!! I price shop and this whole system makes it hard to do that.

In our case, ID purchased and invoiced us. Likewise, he purchased fabrics and had them shipped directly to his workroom and someone came to install them, and I was billed after installation. If I need an estimate he always provides it and its not too different from the final bill for the project.